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/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);
-          setMailsTotal(result.total);
+          setMails(resultMails);
+          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);
-          setMailsTotal(result.total);
+          setMails(!isGrouping && mailsPage > 1 ? (prev) => [...(prev ?? []), ...resultMails] : resultMails);
+          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
-      .flatMap((m) => m.settings_pages)
+    () => (manifests || [])
+      .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 {