fix(frontend): E2E-Test-Suite vollständig grün machen

- Robuster gegen undefined API-Daten in Mail, ContactDetail, ContactsList, Settings, Sidebar
- E2E-Mocks korrigiert für Kontakt-Detail, Mail-Liste/Folders und Plugin-Toggle
- Auth-Store mit persist-Middleware für E2E-Login
- test-results/ in .gitignore aufgenommen

Playwright E2E: 34/34 passed

frontend/.gitignore

@@ -7,3 +7,4 @@ dist/
 coverage/
 .vitest/
 *.log
+test-results/

frontend/e2e/helpers.ts

@@ -66,37 +66,62 @@ export const MOCK_MAIL_ACCOUNTS = [
     smtp_host: 'smtp.test.test',
     smtp_port: 587,
     is_shared: false,
+    is_active: true,
   },
 ];
 
 export const MOCK_MAIL_FOLDERS = [
-  { id: 'folder-001', name: 'INBOX', unread_count: 3, account_id: 'acc-001' },
+  { id: 'folder-001', name: 'INBOX', imap_name: 'INBOX', parent_id: null, unread_count: 3, total_count: 2, account_id: 'acc-001' },
-  { id: 'folder-002', name: 'Sent', unread_count: 0, account_id: 'acc-001' },
+  { id: 'folder-002', name: 'Sent', imap_name: 'Sent', parent_id: null, unread_count: 0, total_count: 0, account_id: 'acc-001' },
-  { id: 'folder-003', name: 'Drafts', unread_count: 0, account_id: 'acc-001' },
+  { id: 'folder-003', name: 'Drafts', imap_name: 'Drafts', parent_id: null, unread_count: 0, total_count: 0, account_id: 'acc-001' },
 ];
 
 export const MOCK_MAILS = [
   {
     id: 'mail-001',
+    folder_id: 'folder-001',
+    account_id: 'acc-001',
     subject: 'Welcome to LeoCRM',
-    from: 'noreply@leocrm.test',
+    from_address: 'noreply@leocrm.test',
-    to: 'test@leocrm.test',
+    from_name: 'LeoCRM',
+    to_addresses: ['test@leocrm.test'],
+    cc_addresses: [],
+    bcc_addresses: [],
     date: '2026-07-23T10:00:00Z',
     body_text: 'Welcome to LeoCRM! Your account is ready.',
-    is_read: false,
+    body_html: null,
-    flags: [],
+    sanitized_html: null,
+    is_seen: false,
+    is_flagged: false,
+    flag_type: null,
+    is_draft: false,
+    is_answered: false,
+    has_attachments: false,
     attachments: [],
+    labels: [],
   },
   {
     id: 'mail-002',
+    folder_id: 'folder-001',
+    account_id: 'acc-001',
     subject: 'Meeting Tomorrow',
-    from: 'boss@leocrm.test',
+    from_address: 'boss@leocrm.test',
-    to: 'test@leocrm.test',
+    from_name: 'Boss',
+    to_addresses: ['test@leocrm.test'],
+    cc_addresses: [],
+    bcc_addresses: [],
     date: '2026-07-23T09:00:00Z',
     body_text: 'Don\'t forget the meeting tomorrow at 10 AM.',
-    is_read: true,
+    body_html: null,
-    flags: [],
+    sanitized_html: null,
+    is_seen: true,
+    is_flagged: false,
+    flag_type: null,
+    is_draft: false,
+    is_answered: false,
+    has_attachments: false,
     attachments: [],
+    labels: [],
   },
 ];
 
@@ -188,13 +213,38 @@ export const MOCK_SEARCH_RESULTS = {
  * Call this in beforeEach to set up a fully mocked environment.
  */
 export async function setupApiMocks(page: Page) {
-  // Auth: login
+  await page.route('**/api/v1/**', (route) => {
-  await page.route('**/api/v1/auth/login', (route) => {
+    const req = route.request();
-    route.fulfill({
+    const url = new URL(req.url());
-      status: 200,
+    const method = req.method();
-      contentType: 'application/json',
+    const pathname = url.pathname;
-      body: JSON.stringify({
+
-        user: {
+    // Auth endpoints
+    if (pathname === '/api/v1/auth/login') {
+      return route.fulfill({
+        status: 200,
+        contentType: 'application/json',
+        body: JSON.stringify({
+          user: {
+            id: TEST_USER.id,
+            email: TEST_USER.email,
+            first_name: TEST_USER.firstName,
+            last_name: TEST_USER.lastName,
+            role: TEST_USER.role,
+            tenants: [TEST_TENANT],
+            permissions: ['*'],
+            is_system_admin: true,
+          },
+          csrf_token: 'mock-csrf-token',
+        }),
+      });
+    }
+
+    if (pathname === '/api/v1/auth/me') {
+      return route.fulfill({
+        status: 200,
+        contentType: 'application/json',
+        body: JSON.stringify({
           id: TEST_USER.id,
           email: TEST_USER.email,
           first_name: TEST_USER.firstName,
@@ -203,320 +253,214 @@ export async function setupApiMocks(page: Page) {
           tenants: [TEST_TENANT],
           permissions: ['*'],
           is_system_admin: true,
-        },
-        csrf_token: 'mock-csrf-token',
-      }),
-    });
-  });
-
-  // Auth: me (current user)
-  await page.route('**/api/v1/auth/me', (route) => {
-    route.fulfill({
-      status: 200,
-      contentType: 'application/json',
-      body: JSON.stringify({
-        id: TEST_USER.id,
-        email: TEST_USER.email,
-        first_name: TEST_USER.firstName,
-        last_name: TEST_USER.lastName,
-        role: TEST_USER.role,
-        tenants: [TEST_TENANT],
-        permissions: ['*'],
-        is_system_admin: true,
-      }),
-    });
-  });
-
-  // Auth: logout
-  await page.route('**/api/v1/auth/logout', (route) => {
-    route.fulfill({ status: 200, contentType: 'application/json', body: '{}' });
-  });
-
-  // Contacts list
-  await page.route('**/api/v1/contacts*', (route) => {
-    const url = route.request().url();
-    if (url.includes('/contact_persons')) {
-      route.fulfill({ status: 200, contentType: 'application/json', body: '[]' });
-      return;
-    }
-    if (route.request().method() === 'GET') {
-      route.fulfill({
-        status: 200,
-        contentType: 'application/json',
-        body: JSON.stringify(MOCK_CONTACTS),
-      });
-    } else if (route.request().method() === 'POST') {
-      const body = route.request().postDataJSON();
-      route.fulfill({
-        status: 201,
-        contentType: 'application/json',
-        body: JSON.stringify({
-          id: 'contact-new',
-          contact_persons: [],
-          displayname: body?.name || `${body?.firstname || ''} ${body?.surname || ''}`.trim(),
-          ...body,
         }),
       });
-    } else {
-      route.fulfill({ status: 200, contentType: 'application/json', body: '{}' });
     }
-  });
 
-  // Contact detail
+    if (pathname === '/api/v1/auth/logout') {
-  await page.route('**/api/v1/contacts/*', (route) => {
+      return route.fulfill({ status: 200, contentType: 'application/json', body: '{}' });
-    if (route.request().method() === 'GET') {
-      route.fulfill({
-        status: 200,
-        contentType: 'application/json',
-        body: JSON.stringify(MOCK_CONTACTS.items[0]),
-      });
-    } else if (route.request().method() === 'PUT') {
-      const body = route.request().postDataJSON();
-      route.fulfill({
-        status: 200,
-        contentType: 'application/json',
-        body: JSON.stringify({ ...MOCK_CONTACTS.items[0], ...body }),
-      });
-    } else if (route.request().method() === 'DELETE') {
-      route.fulfill({ status: 204, body: '' });
-    } else {
-      route.continue();
     }
-  });
 
-  // Mail signatures
+    // Contacts
-  await page.route('**/api/v1/mail/signatures*', (route) => {
+    if (pathname.startsWith('/api/v1/contacts')) {
-    if (route.request().method() === 'GET') {
+      if (pathname.includes('/contact_persons')) {
-      route.fulfill({ status: 200, contentType: 'application/json', body: '[]' });
+        return route.fulfill({ status: 200, contentType: 'application/json', body: '[]' });
-    } else {
+      }
-      route.continue();
+      // Contact detail: /api/v1/contacts/<id>
+      const contactsDetailMatch = pathname.match(/^\/api\/v1\/contacts\/([^/]+)$/);
+      if (contactsDetailMatch && method === 'GET') {
+        return route.fulfill({
+          status: 200,
+          contentType: 'application/json',
+          body: JSON.stringify({ ...MOCK_CONTACTS.items[0], id: contactsDetailMatch[1], contact_persons: [] }),
+        });
+      }
+      if (method === 'GET') {
+        return route.fulfill({
+          status: 200,
+          contentType: 'application/json',
+          body: JSON.stringify(MOCK_CONTACTS),
+        });
+      }
+      if (method === 'POST') {
+        const body = req.postDataJSON() || {};
+        return route.fulfill({
+          status: 201,
+          contentType: 'application/json',
+          body: JSON.stringify({
+            id: 'contact-new',
+            contact_persons: [],
+            displayname: body.name || `${body.firstname || ''} ${body.surname || ''}`.trim(),
+            ...body,
+          }),
+        });
+      }
+      if (method === 'PUT') {
+        const body = req.postDataJSON() || {};
+        const id = pathname.split('/').pop() || 'contact-001';
+        return route.fulfill({
+          status: 200,
+          contentType: 'application/json',
+          body: JSON.stringify({ ...MOCK_CONTACTS.items[0], id, ...body }),
+        });
+      }
+      if (method === 'DELETE') {
+        return route.fulfill({ status: 204, body: '' });
+      }
+      return route.fulfill({ status: 200, contentType: 'application/json', body: '{}' });
     }
-  });
 
-  // Mail accounts
+    // Mail
-  await page.route('**/api/v1/mail/accounts*', (route) => {
+    if (pathname === '/api/v1/mail/accounts') {
-    if (route.request().method() === 'GET') {
+      if (method === 'GET') {
-      route.fulfill({
+        return route.fulfill({ status: 200, contentType: 'application/json', body: JSON.stringify(MOCK_MAIL_ACCOUNTS) });
-        status: 200,
+      }
-        contentType: 'application/json',
+      const body = req.postDataJSON() || {};
-        body: JSON.stringify(MOCK_MAIL_ACCOUNTS),
+      return route.fulfill({
-      });
-    } else if (route.request().method() === 'POST') {
-      const body = route.request().postDataJSON();
-      route.fulfill({
         status: 201,
         contentType: 'application/json',
+        body: JSON.stringify({ id: 'acc-new', display_name: body.display_name || body.email, ...body }),
+      });
+    }
+
+    if (pathname === '/api/v1/mail/folders') {
+      return route.fulfill({ status: 200, contentType: 'application/json', body: JSON.stringify(MOCK_MAIL_FOLDERS) });
+    }
+
+    if (pathname === '/api/v1/mail') {
+      // fetchMails — /api/v1/mail?folder_id=...
+      return route.fulfill({
+        status: 200,
+        contentType: 'application/json',
+        body: JSON.stringify({ mails: MOCK_MAILS, total: MOCK_MAILS.length, page: 1, page_size: 25 }),
+      });
+    }
+
+    if (pathname === '/api/v1/mail/search') {
+      return route.fulfill({
+        status: 200,
+        contentType: 'application/json',
+        body: JSON.stringify({ mails: MOCK_MAILS, total: MOCK_MAILS.length, page: 1, page_size: 25 }),
+      });
+    }
+
+    if (pathname.startsWith('/api/v1/mail/signatures')) {
+      return route.fulfill({ status: 200, contentType: 'application/json', body: '[]' });
+    }
+
+    const singleMailMatch = pathname.match(/^\/api\/v1\/mail\/([^/]+)$/);
+    if (singleMailMatch && method === 'GET') {
+      const mailId = singleMailMatch[1];
+      const mail = MOCK_MAILS.find((m) => m.id === mailId) || MOCK_MAILS[0];
+      return route.fulfill({ status: 200, contentType: 'application/json', body: JSON.stringify(mail) });
+    }
+
+    if (pathname.startsWith('/api/v1/mail/')) {
+      return route.fulfill({ status: 200, contentType: 'application/json', body: '{}' });
+    }
+
+    // DMS
+    if (pathname === '/api/v1/dms/folders') {
+      if (method === 'GET') {
+        return route.fulfill({ status: 200, contentType: 'application/json', body: JSON.stringify(MOCK_DMS_FOLDERS) });
+      }
+      const body = req.postDataJSON() || {};
+      return route.fulfill({
+        status: 201,
+        contentType: 'application/json',
+        body: JSON.stringify({ id: 'folder-new', name: body.name, parent_id: body.parent_id ?? null }),
+      });
+    }
+
+    if (pathname === '/api/v1/dms/files') {
+      return route.fulfill({ status: 200, contentType: 'application/json', body: JSON.stringify(MOCK_DMS_FILES) });
+    }
+
+    if (pathname.startsWith('/api/v1/dms/')) {
+      return route.fulfill({ status: 200, contentType: 'application/json', body: '[]' });
+    }
+
+    // Calendar
+    if (pathname === '/api/v1/calendars') {
+      return route.fulfill({ status: 200, contentType: 'application/json', body: JSON.stringify(MOCK_CALENDARS) });
+    }
+
+    if (pathname === '/api/v1/calendar/entries') {
+      if (method === 'GET') {
+        return route.fulfill({ status: 200, contentType: 'application/json', body: JSON.stringify(MOCK_CALENDAR_ENTRIES) });
+      }
+      const body = req.postDataJSON() || {};
+      return route.fulfill({ status: 201, contentType: 'application/json', body: JSON.stringify({ id: 'entry-new', ...body }) });
+    }
+
+    if (pathname === '/api/v1/calendar/kanban') {
+      return route.fulfill({
+        status: 200,
+        contentType: 'application/json',
         body: JSON.stringify({
-          id: 'acc-new',
+          open: MOCK_CALENDAR_ENTRIES,
-          display_name: body?.display_name || body?.email,
+          in_progress: [],
-          ...body,
+          done: [],
+          cancelled: [],
         }),
       });
-    } else {
-      route.continue();
     }
-  });
 
-  // Mail folders (API calls /mail/folders?account_id=...)
+    // Plugins
-  await page.route('**/api/v1/mail/folders*', (route) => {
+    if (pathname === '/api/v1/plugins/active-manifests' || pathname === '/api/v1/plugins') {
-    if (route.request().method() === 'GET') {
+      if (method === 'GET') {
-      route.fulfill({
+        return route.fulfill({
-        status: 200,
+          status: 200,
-        contentType: 'application/json',
+          contentType: 'application/json',
-        body: JSON.stringify(MOCK_MAIL_FOLDERS),
+          body: JSON.stringify({ plugins: MOCK_PLUGINS, total: MOCK_PLUGINS.length }),
-      });
+        });
-    } else {
+      }
-      route.continue();
+      return route.fulfill({ status: 200, contentType: 'application/json', body: '{}' });
     }
-  });
 
-  // Mail list (API calls /mail/mails?account_id=...&folder_id=...)
+    const pluginToggleMatch = pathname.match(/^\/api\/v1\/plugins\/([^/]+)\/(activate|deactivate)$/);
-  await page.route('**/api/v1/mail/mails*', (route) => {
+    if (pluginToggleMatch) {
-    if (route.request().method() === 'GET') {
+      const [, slug, action] = pluginToggleMatch;
-      route.fulfill({
+      const plugin = MOCK_PLUGINS.find((p) => p.name === slug);
-        status: 200,
+      if (plugin) {
-        contentType: 'application/json',
+        plugin.active = action === 'activate';
-        body: JSON.stringify({ items: MOCK_MAILS, total: MOCK_MAILS.length }),
+        plugin.status = action === 'activate' ? 'active' : 'inactive';
-      });
+      }
-    } else {
+      return route.fulfill({ status: 200, contentType: 'application/json', body: '{}' });
-      route.continue();
     }
-  });
 
-  // Mail detail
+    // Search
-  await page.route('**/api/v1/mail/*', (route) => {
+    if (pathname === '/api/v1/search') {
-    if (route.request().method() === 'GET') {
+      if (method === 'POST') {
-      route.fulfill({
+        return route.fulfill({
-        status: 200,
+          status: 200,
-        contentType: 'application/json',
+          contentType: 'application/json',
-        body: JSON.stringify(MOCK_MAILS[0]),
+          body: JSON.stringify({
-      });
+            results: [
-    } else {
+              { type: 'contact', id: 'contact-001', name: 'TechCorp GmbH', description: 'Company in Berlin', url: '/contacts/contact-001' },
-      route.continue();
+              { type: 'mail', id: 'mail-001', name: 'Welcome to LeoCRM', description: 'Welcome email', url: '/mail/mail-001' },
+            ],
+            facets: {},
+            summary: '2 results',
+          }),
+        });
+      }
+      return route.fulfill({ status: 200, contentType: 'application/json', body: JSON.stringify({ results: [], facets: {}, summary: '' }) });
     }
-  });
 
-  // DMS folders
+    // User preferences
-  await page.route('**/api/v1/dms/folders*', (route) => {
+    if (pathname.startsWith('/api/v1/user/preferences')) {
-    if (route.request().method() === 'GET') {
+      return route.fulfill({ status: 200, contentType: 'application/json', body: '{}' });
-      route.fulfill({
-        status: 200,
-        contentType: 'application/json',
-        body: JSON.stringify(MOCK_DMS_FOLDERS),
-      });
-    } else if (route.request().method() === 'POST') {
-      const body = route.request().postDataJSON();
-      route.fulfill({
-        status: 201,
-        contentType: 'application/json',
-        body: JSON.stringify({ id: 'folder-new', name: body?.name, parent_id: body?.parent_id ?? null }),
-      });
-    } else {
-      route.continue();
     }
-  });
 
-  // DMS files
+    // Fallback: empty array/object for any other API call
-  await page.route('**/api/v1/dms/files*', (route) => {
+    return route.fulfill({ status: 200, contentType: 'application/json', body: '[]' });
-    if (route.request().method() === 'GET') {
-      route.fulfill({
-        status: 200,
-        contentType: 'application/json',
-        body: JSON.stringify(MOCK_DMS_FILES),
-      });
-    } else {
-      route.continue();
-    }
-  });
-
-  // DMS shared files
-  await page.route('**/api/v1/dms/shared*', (route) => {
-    route.fulfill({ status: 200, contentType: 'application/json', body: '[]' });
-  });
-
-  // Calendar list (API calls /calendars, not /calendar/calendars)
-  await page.route('**/api/v1/calendars*', (route) => {
-    if (route.request().method() === 'GET') {
-      route.fulfill({
-        status: 200,
-        contentType: 'application/json',
-        body: JSON.stringify(MOCK_CALENDARS),
-      });
-    } else {
-      route.continue();
-    }
-  });
-
-  // Calendar entries
-  await page.route('**/api/v1/calendar/entries*', (route) => {
-    if (route.request().method() === 'GET') {
-      route.fulfill({
-        status: 200,
-        contentType: 'application/json',
-        body: JSON.stringify(MOCK_CALENDAR_ENTRIES),
-    });
-    } else if (route.request().method() === 'POST') {
-      const body = route.request().postDataJSON();
-      route.fulfill({
-        status: 201,
-        contentType: 'application/json',
-        body: JSON.stringify({ id: 'entry-new', ...body }),
-      });
-    } else {
-      route.continue();
-    }
-  });
-
-  // Calendar kanban
-  await page.route('**/api/v1/calendar/kanban*', (route) => {
-    route.fulfill({
-      status: 200,
-      contentType: 'application/json',
-      body: JSON.stringify({
-        open: MOCK_CALENDAR_ENTRIES,
-        in_progress: [],
-        done: [],
-        cancelled: [],
-      }),
-    });
-  });
-
-  // Plugins
-  await page.route('**/api/v1/plugins*', (route) => {
-    const url = route.request().url();
-    if (url.includes('/active-manifests')) {
-      route.fulfill({
-        status: 200,
-        contentType: 'application/json',
-        body: JSON.stringify({ plugins: MOCK_PLUGINS, total: MOCK_PLUGINS.length }),
-      });
-      return;
-    }
-    if (route.request().method() === 'GET') {
-      // GET /plugins returns { plugins: Plugin[], total: number }
-      route.fulfill({
-        status: 200,
-        contentType: 'application/json',
-        body: JSON.stringify({ plugins: MOCK_PLUGINS, total: MOCK_PLUGINS.length }),
-      });
-    } else if (route.request().method() === 'POST') {
-      route.fulfill({ status: 200, contentType: 'application/json', body: '{}' });
-    } else {
-      route.continue();
-    }
-  });
-
-  // Plugin activate/deactivate
-  await page.route('**/api/v1/plugins/*/activate', (route) => {
-    route.fulfill({ status: 200, contentType: 'application/json', body: '{}' });
-  });
-  await page.route('**/api/v1/plugins/*/deactivate', (route) => {
-    route.fulfill({ status: 200, contentType: 'application/json', body: '{}' });
-  });
-
-  // Search (API uses POST to /search)
-  await page.route('**/api/v1/search*', (route) => {
-    if (route.request().method() === 'POST') {
-      route.fulfill({
-        status: 200,
-        contentType: 'application/json',
-        body: JSON.stringify({ results: [
-          { type: 'contact', id: 'contact-001', name: 'TechCorp GmbH', description: 'Company in Berlin', url: '/contacts/contact-001' },
-          { type: 'mail', id: 'mail-001', name: 'Welcome to LeoCRM', description: 'Welcome email', url: '/mail/mail-001' },
-        ], facets: {}, summary: '2 results' }),
-      });
-    } else if (route.request().method() === 'GET') {
-      route.fulfill({
-        status: 200,
-        contentType: 'application/json',
-        body: JSON.stringify({ results: [], facets: {}, summary: '' }),
-      });
-    } else {
-      route.continue();
-    }
-  });
-
-  // User preferences
-  await page.route('**/api/v1/user/preferences*', (route) => {
-    route.fulfill({ status: 200, contentType: 'application/json', body: '{}' });
-  });
-
-  // Generic catch-all for other API endpoints
-  await page.route('**/api/v1/**', (route) => {
-    if (!route.request().url().includes('/auth/') &&
-        !route.request().url().includes('/contacts') &&
-        !route.request().url().includes('/mail/') &&
-        !route.request().url().includes('/dms/') &&
-        !route.request().url().includes('/calendar/') &&
-        !route.request().url().includes('/plugins') &&
-        !route.request().url().includes('/search')) {
-      route.fulfill({ status: 200, contentType: 'application/json', body: '[]' });
-    } else {
-      route.continue();
-    }
   });
 }
 
+/**
+ * Perform login via the login form.}
+
 /**
  * Perform login via the login form.
  * Assumes API mocks are already set up.

frontend/e2e/mail.spec.ts

@@ -11,14 +11,15 @@ test.describe('Mail E2E', () => {
     await navigateTo(page, '/mail');
 
     // Mail page should load - check for folder tree or loading state
-    await expect(page.locator('[data-testid="folder-tree-list"], [data-testid="folder-tree-loading"], [data-testid="folder-tree-empty"]')).toBeVisible({ timeout: 15_000 });
+    // .first() because the responsive layout renders the tree in both desktop and mobile panes.
+    await expect(page.locator('[data-testid="folder-tree-list"], [data-testid="folder-tree-loading"], [data-testid="folder-tree-empty"]').first()).toBeVisible({ timeout: 15_000 });
   });
 
   test('mail list shows emails when folder is selected', async ({ page }) => {
     await navigateTo(page, '/mail');
 
     // Wait for folder tree
-    await expect(page.locator('[data-testid="folder-tree-list"], [data-testid="folder-tree-loading"], [data-testid="folder-tree-empty"]')).toBeVisible({ timeout: 15_000 });
+    await expect(page.locator('[data-testid="folder-tree-list"], [data-testid="folder-tree-loading"], [data-testid="folder-tree-empty"]').first()).toBeVisible({ timeout: 15_000 });
 
     // Click on first folder if available
     const folder = page.locator('[data-testid^="folder-"]').first();
@@ -26,7 +27,7 @@ test.describe('Mail E2E', () => {
       await folder.click();
 
       // Mail list should appear
-      await expect(page.locator('[data-testid="mail-list"], [data-testid="mail-list-loading"], [data-testid="mail-list-empty"]')).toBeVisible({ timeout: 10_000 });
+      await expect(page.locator('[data-testid="mail-list"], [data-testid="mail-list-loading"], [data-testid="mail-list-empty"]').first()).toBeVisible({ timeout: 10_000 });
     }
   });
 
@@ -34,14 +35,14 @@ test.describe('Mail E2E', () => {
     await navigateTo(page, '/mail');
 
     // Wait for folder tree and click first folder
-    await expect(page.locator('[data-testid="folder-tree-list"], [data-testid="folder-tree-loading"], [data-testid="folder-tree-empty"]')).toBeVisible({ timeout: 15_000 });
+    await expect(page.locator('[data-testid="folder-tree-list"], [data-testid="folder-tree-loading"], [data-testid="folder-tree-empty"]').first()).toBeVisible({ timeout: 15_000 });
 
     const folder = page.locator('[data-testid^="folder-"]').first();
     if (await folder.isVisible({ timeout: 5_000 })) {
       await folder.click();
 
       // Wait for mail list
-      await expect(page.locator('[data-testid="mail-list"], [data-testid="mail-list-loading"], [data-testid="mail-list-empty"]')).toBeVisible({ timeout: 10_000 });
+      await expect(page.locator('[data-testid="mail-list"], [data-testid="mail-list-loading"], [data-testid="mail-list-empty"]').first()).toBeVisible({ timeout: 10_000 });
 
       // Click first mail if available
       const mailItem = page.locator('[data-testid^="mail-item-"]').first();
@@ -49,7 +50,7 @@ test.describe('Mail E2E', () => {
         await mailItem.click();
 
         // Mail detail should appear
-        await expect(page.locator('[data-testid="mail-detail"], [data-testid="mail-detail-loading"], [data-testid="mail-detail-empty"]')).toBeVisible({ timeout: 10_000 });
+        await expect(page.locator('[data-testid="mail-detail"], [data-testid="mail-detail-loading"], [data-testid="mail-detail-empty"]').first()).toBeVisible({ timeout: 10_000 });
       }
     }
   });

frontend/e2e/plugin-toggle.spec.ts

@@ -62,6 +62,6 @@ test.describe('Plugin Toggle E2E', () => {
     await expect(page.locator('[data-testid="settings-plugins-page"]')).toBeVisible({ timeout: 10_000 });
 
     // Upload and URL install options should be present
-    await expect(page.locator('[data-testid="plugin-zip-upload-input"], [data-testid="plugin-upload-btn"], [data-testid="plugin-url-input"], [data-testid="plugin-install-url-btn"]')).toBeVisible({ timeout: 10_000 });
+    await expect(page.locator('[data-testid="plugin-zip-upload-input"], [data-testid="plugin-upload-btn"], [data-testid="plugin-url-input"], [data-testid="plugin-install-url-btn"]').first()).toBeVisible({ timeout: 10_000 });
   });
 });

frontend/e2e/search.spec.ts

@@ -25,7 +25,7 @@ test.describe('Global Search E2E', () => {
     await page.locator('[data-testid="search-submit-btn"]').click();
 
     // Wait for results
-    await expect(page.locator('[data-testid="search-results-list"], [data-testid="search-results-all"]')).toBeVisible({ timeout: 10_000 });
+    await expect(page.locator('[data-testid="search-results-list"], [data-testid="search-results-all"]').first()).toBeVisible({ timeout: 10_000 });
 
     // Should show at least one result (or empty state if mock doesn't match exactly)
     const resultItem = page.locator('[data-testid^="search-result-"]').first();

frontend/src/components/contacts/ContactDetail.tsx

@@ -33,6 +33,7 @@ export interface ContactDetailProps {
   loading?: boolean;
   onEdit?: () => void;
   onDeleted: () => void;
+  dataTestId?: string;
 }
 
 function Field({ label, value, fieldName }: { label: string; value?: string | null; fieldName?: string }) {
@@ -156,7 +157,7 @@ function getIcon(name: string): React.ReactNode {
   return Icon ? <Icon className="h-4 w-4" /> : <LucideIcons.FileText className="h-4 w-4" />;
 }
 
-export function ContactDetail({ contact, loading, onEdit, onDeleted }: ContactDetailProps) {
+export function ContactDetail({ contact, loading, onEdit, onDeleted, dataTestId = 'contact-detail' }: ContactDetailProps) {
   const { t } = useTranslation();
   const toast = useToast();
   const deleteMutation = useDeleteUnifiedContact();
@@ -173,9 +174,9 @@ export function ContactDetail({ contact, loading, onEdit, onDeleted }: ContactDe
   const [activeTab, setActiveTab] = useState('details');
   const manifests = usePluginStore(s => s.manifests);
   const pluginTabs = useMemo(
-    () => manifests
+    () => (manifests || [])
-      .flatMap((m) => m.detail_tabs)
+      .flatMap((m) => (Array.isArray(m.detail_tabs) ? m.detail_tabs : []))
-      .filter((t) => t.entity_type === 'contact')
+      .filter((t): t is NonNullable<typeof t> => !!t && t.entity_type === 'contact')
       .sort((a, b) => a.order - b.order),
     [manifests]
   );
@@ -283,7 +284,7 @@ export function ContactDetail({ contact, loading, onEdit, onDeleted }: ContactDe
   ];
 
   return (
-    <div className="overflow-y-auto h-full" data-testid="contact-detail">
+    <div className="overflow-y-auto h-full" data-testid={dataTestId}>
       {/* Header */}
       <div className="flex items-center justify-between px-4 py-3 border-b border-secondary-200 sticky top-0 bg-white z-10">
         <div className="flex items-center gap-3 min-w-0">

frontend/src/components/layout/Sidebar.tsx

@@ -87,9 +87,9 @@ export function Sidebar() {
       permission: item.to === '/dashboard' ? 'dashboard:read' : item.to === '/contacts' ? 'contacts:read' : undefined,
     }));
 
-    const pluginItems = manifests
+    const pluginItems = (manifests || [])
-      .flatMap((m) => m.menu_items)
+      .flatMap((m) => (Array.isArray(m.menu_items) ? m.menu_items : []))
-      .filter(item => !item.permission || canAccess(item.permission))
+      .filter((item): item is NonNullable<typeof item> => !!item && (!item.permission || canAccess(item.permission)))
       .map(item => ({
         path: item.path,
         labelKey: item.label_key,

frontend/src/components/mail/MailDetail.tsx

@@ -110,12 +110,12 @@ export function MailDetail({
           </div>
           <div className="flex flex-col sm:flex-row sm:gap-2">
             <span className="font-medium text-secondary-500 flex-shrink-0">{t('mail.to')}:</span>
-            <span className="break-words">{mail.to_addresses.join(', ')}</span>
+            <span className="break-words">{(mail.to_addresses ?? []).join(', ')}</span>
           </div>
-          {mail.cc_addresses.length > 0 && (
+          {mail.cc_addresses && mail.cc_addresses.length > 0 && (
             <div className="flex flex-col sm:flex-row sm:gap-2">
               <span className="font-medium text-secondary-500 flex-shrink-0">{t('mail.cc')}:</span>
-              <span className="break-words">{mail.cc_addresses.join(', ')}</span>
+              <span className="break-words">{(mail.cc_addresses ?? []).join(', ')}</span>
             </div>
           )}
           <div className="flex flex-col sm:flex-row sm:gap-2">

frontend/src/components/mail/MailFilterPanel.tsx

@@ -151,7 +151,7 @@ function matchesCondition(mail: any, cond: FilterCondition): boolean {
 }
 
 export function applyFilters(mails: any[], filters: FilterState): any[] {
-  if (!filters.conditions.length) return mails;
+  if (!(filters.conditions?.length ?? 0)) return mails;
   if (filters.logic === 'AND') {
     return mails.filter((m) => filters.conditions.every((cond) => matchesCondition(m, cond)));
   } else {
@@ -208,7 +208,7 @@ export function MailFilterPanel({ filters, onFiltersChange, savedFilters = [], o
     setOpen(!open);
   };
 
-  const activeCount = filters.conditions.length;
+  const activeCount = filters.conditions?.length ?? 0;
 
   const addCondition = () => {
     onFiltersChange({
@@ -248,7 +248,7 @@ export function MailFilterPanel({ filters, onFiltersChange, savedFilters = [], o
 
   const handleSaveFilter = () => {
     if (!onSaveFilter) return;
-    if (filters.conditions.length === 0) return;
+    if ((filters.conditions?.length ?? 0) === 0) return;
     const name = window.prompt('Name für diesen Filter:', 'Mein Filter');
     if (!name) return;
     onSaveFilter(name, { ...filters, conditions: filters.conditions.map((c) => ({ ...c })) });
@@ -345,7 +345,7 @@ export function MailFilterPanel({ filters, onFiltersChange, savedFilters = [], o
           )}
 
           {/* Saved filters */}
-          {savedFilters.length > 0 && (
+          {(savedFilters?.length ?? 0) > 0 && (
             <div className="px-4 py-2 border-b border-secondary-100">
               <div className="text-[10px] font-semibold uppercase tracking-wide text-secondary-400 mb-1.5">Gespeicherte Filter</div>
               <div className="space-y-0.5">
@@ -366,7 +366,7 @@ export function MailFilterPanel({ filters, onFiltersChange, savedFilters = [], o
 
           {/* Filter rows */}
           <div className="px-4 py-3 space-y-2">
-            {filters.conditions.length === 0 && (
+            {(filters.conditions?.length ?? 0) === 0 && (
               <div className="text-center py-6 text-xs text-secondary-400">
                 Keine Filter aktiv. Klicke unten um eine Bedingung hinzuzufügen.
               </div>

frontend/src/components/mail/MailFolderTree.tsx

@@ -301,7 +301,7 @@ export function MailFolderTree({ accounts, folders, selectedFolderId, onSelect,
     );
   }
 
-  if (accounts.length === 0) {
+  if ((accounts?.length ?? 0) === 0) {
     return (
       <EmptyState
         title={t('mail.noFolders')}

frontend/src/components/mail/MailGroupPanel.tsx

@@ -73,7 +73,7 @@ export interface GroupedMails {
 }
 
 export function applyGrouping(mails: any[], groupState: GroupState): GroupedMails[] {
-  if (!groupState.conditions.length) return [{ key: 'all', label: 'Alle', mails }];
+  if (!(groupState.conditions?.length ?? 0)) return [{ key: 'all', label: 'Alle', mails }];
   const defs = GROUP_FIELDS;
 
   function groupRecursive(items: any[], conditions: GroupCondition[], depth: number): GroupedMails[] {
@@ -139,7 +139,7 @@ export function MailGroupPanel({ groupState, onGroupChange }: MailGroupPanelProp
     setOpen(!open);
   };
 
-  const activeCount = groupState.conditions.length;
+  const activeCount = groupState.conditions?.length ?? 0;
 
   const addCondition = () => {
     onGroupChange({ conditions: [...groupState.conditions, { id: newGroupId(), field: 'from' }] });

frontend/src/components/mail/MailList.tsx

@@ -52,8 +52,8 @@ function GroupSection({
   const hasSubGroups = group.subGroups && group.subGroups.length > 0;
   // Count total mails including subGroups
   const totalCount = hasSubGroups
-    ? group.subGroups!.reduce((sum, sub) => sum + sub.mails.length, 0)
+    ? group.subGroups!.reduce((sum, sub) => sum + (sub.mails?.length ?? 0), 0)
-    : group.mails.length;
+    : (group.mails?.length ?? 0);
 
   return (
     <li className="bg-secondary-50/30">
@@ -110,7 +110,7 @@ export function MailList({
   hasMore = false,
 }: MailListProps) {
   const { t } = useTranslation();
-  const allSelected = mails.length > 0 && mails.every((m) => selectedMailIds.has(m.id));
+  const allSelected = (mails?.length ?? 0) > 0 && mails.every((m) => selectedMailIds.has(m.id));
   const scrollRef = useRef<HTMLUListElement>(null);
 
   // Infinite scroll handler
@@ -121,7 +121,7 @@ export function MailList({
     }
   };
 
-  if (loading && mails.length === 0) {
+  if (loading && (mails?.length ?? 0) === 0) {
     return (
       <div className="flex items-center justify-center py-12" data-testid="mail-list-loading">
         <Loader2 className="animate-spin h-5 w-5 text-secondary-400" aria-hidden="true" />
@@ -130,7 +130,7 @@ export function MailList({
     );
   }
 
-  if (mails.length === 0) {
+  if ((mails?.length ?? 0) === 0) {
     return (
       <EmptyState
         title={t('mail.noMails')}
@@ -228,7 +228,7 @@ export function MailList({
             </span>
           )}
         </div>
-        {loading && mails.length > 0 && <Loader2 className="w-4 h-4 animate-spin text-secondary-400" />}
+        {loading && (mails?.length ?? 0) > 0 && <Loader2 className="w-4 h-4 animate-spin text-secondary-400" />}
       </div>
 
       {/* Mail list — infinite scroll with optional grouping */}
@@ -254,7 +254,7 @@ export function MailList({
         ) : (
           mails.map((mail) => renderMailItem(mail))
         )}
-        {loading && mails.length > 0 && (
+        {loading && (mails?.length ?? 0) > 0 && (
           <li className="flex items-center justify-center py-4">
             <Loader2 className="w-5 h-5 animate-spin text-secondary-400" />
           </li>

frontend/src/components/mail/MailSortPanel.tsx

@@ -60,7 +60,7 @@ function compareValues(a: any, b: any, fieldType: FieldType): number {
 }
 
 export function applySorting(mails: any[], sortState: SortState): any[] {
-  if (!sortState.conditions.length) return mails;
+  if (!(sortState.conditions?.length ?? 0)) return mails;
   const sorted = [...mails];
   sorted.sort((a, b) => {
     for (const cond of sortState.conditions) {
@@ -111,7 +111,7 @@ export function MailSortPanel({ sortState, onSortChange }: MailSortPanelProps) {
     setOpen(!open);
   };
 
-  const activeCount = sortState.conditions.length;
+  const activeCount = sortState.conditions?.length ?? 0;
 
   const addCondition = () => {
     onSortChange({

frontend/src/pages/ContactsList.tsx

@@ -70,6 +70,7 @@ export function ContactsListPage() {
   const [saveViewDialogOpen, setSaveViewDialogOpen] = useState(false);
   const [selectedContactIds, setSelectedContactIds] = useState<Set<string>>(new Set());
   const openWindow = useWindowStore((s) => s.openWindow);
+  const closeWindow = useWindowStore((s) => s.closeWindow);
 
   // Bulk action mutations
   const deleteContactMut = useDeleteUnifiedContact();
@@ -223,32 +224,32 @@ export function ContactsListPage() {
 
   // Handle create
   const handleCreate = useCallback(() => {
-    openWindow({
+    const windowId = openWindow({
       title: t('contacts.create'),
       type: 'contact-create',
       component: ContactEditForm,
       componentProps: {
-        onClose: () => {},
+        onClose: () => closeWindow(windowId),
         onSaved: handleSaved,
       },
     });
-  }, [openWindow, t, handleSaved]);
+  }, [openWindow, closeWindow, t, handleSaved]);
 
   // Handle edit
   const handleEdit = useCallback(() => {
     if (selectedContact) {
-      openWindow({
+      const windowId = openWindow({
         title: t('contacts.edit'),
         type: 'contact-edit',
         component: ContactEditForm,
         componentProps: {
           contact: selectedContact,
-          onClose: () => {},
+          onClose: () => closeWindow(windowId),
           onSaved: handleSaved,
         },
       });
     }
-  }, [selectedContact, openWindow, t, handleSaved]);
+  }, [selectedContact, openWindow, closeWindow, t, handleSaved]);
 
   // Handle delete (from detail)
   const handleDeleted = useCallback(() => {
@@ -747,6 +748,7 @@ export function ContactsListPage() {
               loading={loadingDetail}
               onEdit={handleEdit}
               onDeleted={handleDeleted}
+              dataTestId="contact-detail-mobile"
             />
           </div>
         )}

frontend/src/pages/Mail.tsx

@@ -99,10 +99,10 @@ export function MailPage() {
   // Apply filter + sort to mails before rendering
   const processedMails = useMemo(() => {
     let result = mails;
-    if (mailFilterState.conditions.length > 0) {
+    if ((mailFilterState.conditions || []).length > 0) {
       result = applyMailFilters(result, mailFilterState);
     }
-    if (mailSortState.conditions.length > 0) {
+    if ((mailSortState.conditions || []).length > 0) {
       result = applyMailSorting(result, mailSortState);
     }
     return result;
@@ -110,7 +110,7 @@ export function MailPage() {
 
   // Apply grouping after filter+sort
   const groupedMails = useMemo(() => {
-    if (mailGroupState.conditions.length === 0) return null;
+    if ((mailGroupState.conditions || []).length === 0) return null;
     return applyMailGrouping(processedMails, mailGroupState);
   }, [processedMails, mailGroupState]);
 
@@ -153,7 +153,7 @@ export function MailPage() {
 
   // Load folders for ALL accounts
   const loadAllFolders = useCallback(async () => {
-    if (accounts.length === 0) return;
+    if ((accounts?.length ?? 0) === 0) return;
     setLoadingFolders(true);
     try {
       const allFolders: MailFolder[] = [];
@@ -175,7 +175,7 @@ export function MailPage() {
 
   // Auto-select first folder when folders are loaded
   useEffect(() => {
-    if (folders.length > 0 && !selectedFolderId) {
+    if ((folders?.length ?? 0) > 0 && !selectedFolderId) {
       setSelectedFolderId(folders[0].id);
       setSelectedAccountId(folders[0].account_id);
     }
@@ -189,21 +189,25 @@ export function MailPage() {
     try {
       if (searchQuery.trim()) {
         const result = await searchMails(searchQuery);
+        const resultMails = result.mails ?? [];
+        const resultTotal = result.total ?? 0;
         // Only update if still on the same folder
         if (selectedFolderIdRef.current === currentFolderId) {
-          setMails(result.mails);
+          setMails(resultMails);
-          setMailsTotal(result.total);
+          setMailsTotal(resultTotal);
         }
       } else {
         // When grouping is active, load all mails at once (no pagination)
-        const isGrouping = mailGroupState.conditions.length > 0;
+        const isGrouping = (mailGroupState.conditions || []).length > 0;
         const pageToLoad = isGrouping ? 1 : mailsPage;
         const result = await fetchMails(currentFolderId, pageToLoad, sortBy, sortOrder, isGrouping ? 10000 : undefined);
+        const resultMails = result.mails ?? [];
+        const resultTotal = result.total ?? 0;
         // Only update if still on the same folder
         if (selectedFolderIdRef.current === currentFolderId) {
           // Append for infinite scroll (page > 1), replace on page 1 or folder change or grouping
-          setMails(!isGrouping && mailsPage > 1 ? (prev) => [...prev, ...result.mails] : result.mails);
+          setMails(!isGrouping && mailsPage > 1 ? (prev) => [...(prev ?? []), ...resultMails] : resultMails);
-          setMailsTotal(result.total);
+          setMailsTotal(resultTotal);
         }
       }
     } catch (err) {
@@ -851,7 +855,7 @@ export function MailPage() {
     );
   }
 
-  if (accounts.length === 0) {
+  if ((accounts?.length ?? 0) === 0) {
     return (
       <div className="p-6 max-w-7xl mx-auto" data-testid="mail-page">
         <EmptyState
@@ -911,11 +915,11 @@ export function MailPage() {
             onToggleSelect={handleToggleSelect}
             onSelectAll={handleSelectAll}
             onLoadMore={() => {
-              if (mails.length < mailsTotal) {
+              if ((mails?.length ?? 0) < mailsTotal) {
                 setMailsPage((p) => p + 1);
               }
             }}
-            hasMore={mailGroupState.conditions.length === 0 && mails.length < mailsTotal}
+            hasMore={(mailGroupState.conditions || []).length === 0 && (mails?.length ?? 0) < mailsTotal}
           />
         </ResizablePanel>
 
@@ -982,11 +986,11 @@ export function MailPage() {
               onToggleSelect={handleToggleSelect}
               onSelectAll={handleSelectAll}
               onLoadMore={() => {
-                if (mails.length < mailsTotal) {
+                if ((mails?.length ?? 0) < mailsTotal) {
                   setMailsPage((p) => p + 1);
                 }
               }}
-              hasMore={mailGroupState.conditions.length === 0 && mails.length < mailsTotal}
+              hasMore={(mailGroupState.conditions || []).length === 0 && (mails?.length ?? 0) < mailsTotal}
             />
           </div>
         )}

frontend/src/pages/Settings.tsx

@@ -8,8 +8,9 @@ export function SettingsPage() {
   const { t } = useTranslation();
   const manifests = usePluginStore(s => s.manifests);
   const pluginSettingsPages = useMemo(
-    () => manifests
+    () => (manifests || [])
-      .flatMap((m) => m.settings_pages)
+      .flatMap((m) => (Array.isArray(m.settings_pages) ? m.settings_pages : []))
+      .filter((p): p is NonNullable<typeof p> => !!p && !!p.path)
       .sort((a, b) => a.order - b.order),
     [manifests]
   );

frontend/src/pages/SettingsPlugins.tsx

@@ -180,7 +180,9 @@ export function SettingsPluginsPage() {
   const [confirmUninstall, setConfirmUninstall] = useState<Plugin | null>(null);
   const [confirmRemoveData, setConfirmRemoveData] = useState(false);
 
-  const plugins: Plugin[] = data ?? [];
+  const plugins: Plugin[] = Array.isArray(data)
+    ? data
+    : (data as any)?.plugins ?? [];
 
   const handleInstall = async (plugin: Plugin) => {
     try {

frontend/src/store/authStore.ts

@@ -1,4 +1,5 @@
 import { create } from 'zustand';
+import { persist } from 'zustand/middleware';
 
 export interface Tenant {
   id: string;
@@ -34,39 +35,49 @@ export interface AuthState {
 }
 
 export const useAuthStore = create<AuthState>()(
-  (set) => ({
+  persist(
-      user: null,
+    (set) => ({
-      currentTenant: null,
+        user: null,
-      isAuthenticated: false,
+        currentTenant: null,
-      isLoading: false,
+        isAuthenticated: false,
-      error: null,
+        isLoading: false,
-      setUser: (user) =>
+        error: null,
-        set({
+        setUser: (user) =>
-          user,
+          set({
-          isAuthenticated: !!user,
+            user,
-          currentTenant: user?.tenants?.[0] ?? null,
+            isAuthenticated: !!user,
-        }),
+            currentTenant: user?.tenants?.[0] ?? null,
-      setTenant: (tenant) => set({ currentTenant: tenant }),
+          }),
-      setAuthenticated: (authed) => set({ isAuthenticated: authed }),
+        setTenant: (tenant) => set({ currentTenant: tenant }),
-      setLoading: (loading) => set({ isLoading: loading }),
+        setAuthenticated: (authed) => set({ isAuthenticated: authed }),
-      setError: (error) => set({ error }),
+        setLoading: (loading) => set({ isLoading: loading }),
-      setPermissions: (perms, isSystemAdmin, fieldPerms) =>
+        setError: (error) => set({ error }),
-        set((state) => ({
+        setPermissions: (perms, isSystemAdmin, fieldPerms) =>
-          user: state.user
+          set((state) => ({
-            ? {
+            user: state.user
-                ...state.user,
+              ? {
-                permissions: perms,
+                  ...state.user,
-                is_system_admin: isSystemAdmin,
+                  permissions: perms,
-                field_permissions: fieldPerms,
+                  is_system_admin: isSystemAdmin,
-              }
+                  field_permissions: fieldPerms,
-            : null,
+                }
-        })),
+              : null,
-      logout: () =>
+          })),
-        set({
+        logout: () =>
-          user: null,
+          set({
-          currentTenant: null,
+            user: null,
-          isAuthenticated: false,
+            currentTenant: null,
-          error: null,
+            isAuthenticated: false,
-        }),
+            error: null,
-  })
+          }),
+    }),
+    {
+      name: 'auth-store',
+      partialize: (state) => ({
+        user: state.user,
+        currentTenant: state.currentTenant,
+        isAuthenticated: state.isAuthenticated,
+      }),
+    }
+  )
 );