Phase 3: Plugin-UI-System (WordPress-Style)

Backend:
- PluginManifest um 5 neue UI-Felder erweitert: menu_items, page_routes,
  detail_tabs, settings_pages, dashboard_widgets (FrontendMenuItem,
  FrontendPageRoute, FrontendDetailTab, FrontendSettingsPage,
  FrontendDashboardWidget)
- GET /api/v1/plugins/active-manifests Endpoint liefert UI-Manifeste
  aller aktiven Plugins
- Registry.get_active_manifests() + PluginService.get_active_manifests()
- 12 Built-in Plugins mit UI-Manifest-Daten gefuellt (menu_items,
  page_routes, detail_tabs, settings_pages)
- Plugin-Install-System: POST /upload (ZIP), POST /install-url (URL)
  mit Validierung (Manifest, dangerous imports, SQL migrations)

Frontend:
- pluginStore.ts (Zustand) mit PluginUiManifest Typen + Selektoren
- useActivePluginManifests() React Query Hook
- PluginRegistry.tsx — fetcht Manifeste beim App-Start
- PluginLoader.tsx — dynamisches React.lazy() mit ErrorBoundary
- PluginRouteRenderer.tsx — Catch-all fuer Plugin-Routes
- routes/index.tsx — Catch-all Routes fuer Plugin-Pages + Settings
- Sidebar.tsx — dynamische Plugin Menu-Items mit Grouping + Icons
- Settings.tsx — dynamische Plugin Settings-Pages
- ContactDetail.tsx — dynamische Plugin Detail-Tabs mit Permissions
- AppShell.tsx — PluginRegistry Provider eingebunden
- SettingsPlugins.tsx — Install-UI (ZIP Upload + URL Install)
- plugins.ts — useUploadPlugin() + useInstallPluginFromUrl() Hooks

Docs & Templates:
- docs/plugin-development-guide.md — komplette Entwickler-Doku
- templates/plugin-template/ — Boilerplate mit allen Manifest-Feldern

Tests:
- 34 Vitest-Tests (PluginRegistry, PluginLoader, PluginRouteRenderer,
  pluginStore) — alle bestanden
- TSC: keine neuen Errors (nur pre-existing Dms.tsx)

templates/plugin-template/schemas.py

@@ -0,0 +1,50 @@
+"""
+Pydantic schemas for the example plugin.
+
+Customize these for your plugin's API request/response models.
+"""
+
+from __future__ import annotations
+
+from datetime import datetime
+from uuid import UUID
+
+from pydantic import BaseModel, Field
+
+
+class ExampleItemBase(BaseModel):
+    """Base schema for an example item."""
+
+    name: str = Field(..., min_length=1, max_length=200, description="Item name")
+    description: str | None = Field(None, max_length=1000, description="Item description")
+
+
+class ExampleItemCreate(ExampleItemBase):
+    """Schema for creating an example item."""
+    pass
+
+
+class ExampleItemUpdate(BaseModel):
+    """Schema for updating an example item."""
+
+    name: str | None = Field(None, min_length=1, max_length=200)
+    description: str | None = Field(None, max_length=1000)
+
+
+class ExampleItemResponse(ExampleItemBase):
+    """Schema for returning an example item."""
+
+    id: UUID
+    tenant_id: UUID
+    is_active: bool
+    created_at: datetime
+    updated_at: datetime
+
+    model_config = {"from_attributes": True}
+
+
+class ExampleItemListResponse(BaseModel):
+    """Schema for a paginated list of example items."""
+
+    items: list[ExampleItemResponse]
+    total: int