Phase 0 Complete: Tasks 0.7-0.20

- 0.7: UI-Design-Richtlinien (docs/ui-design-guidelines.md, 535 lines)
- 0.8: Theme-Customization Backend (4 theme fields, migration 0023)
- 0.9: Theme-Customization Frontend (SettingsTheme.tsx, themeStore.ts, live preview)
- 0.10: RBAC-Audit (4 plugins secured, 53 routes with require_permission)
- 0.11: LiteLLM-Cleanup (llm_client.py migrated from httpx to litellm)
- 0.12: KI-Agent-Framework docs (plugin-development-guide.md, agent_capabilities field)
- 0.13: Heartbeat configurable (ProactiveSettings, migration 0024, frontend UI)
- 0.14: Unified Search Field-Level RBAC (resolve_permissions + filter_fields_by_permission)
- 0.15: Undo/History-System (EntityHistory model, service, routes, migration 0025, HistoryViewer)
- 0.16: Storage Backend (LocalStorage + S3Storage, DMS/attachments/mail updated)
- 0.17: Import/Export unified Contact fields (firstname, surname, email_1, phone_1)
- 0.18: .gitignore & Config-Cleanup (webui→frontend, python-jose removed, .env untracked)
- 0.19: Mail-Salt Security-Fix (per-account random salt, migration 0026)
- 0.20: AGPL replaced (PyMuPDF→pypdf, OnlyOffice→Collabora, LICENSE + THIRD_PARTY_LICENSES.md)

frontend/src/routes/index.tsx

@@ -29,6 +29,7 @@ import { SettingsNotificationsPage } from '@/pages/SettingsNotifications';
 import { AIAssistantPage } from '@/pages/AIAssistant';
 import { AISettingsPage } from '@/pages/AISettings';
 import { ProactiveAISettings } from '@/pages/ProactiveAISettings';
+import { SettingsThemePage } from '@/pages/SettingsTheme';
 
 const router = createBrowserRouter([
   {
@@ -79,6 +80,7 @@ const router = createBrowserRouter([
           { path: 'notifications', element: <SettingsNotificationsPage /> },
           { path: 'ai', element: <AISettingsPage /> },
           { path: 'ai-proactive', element: <ProactiveAISettings /> },
+          { path: 'theme', element: <SettingsThemePage /> },
         ],
       },
     ],