feat(M1): Universal-MiniApp-Registry — Plugin-Layer, permission fail-closed, Lifecycle, /api/v1/miniapps

- app/plugins/miniapp_registry.py: Registry aus kommunikation in Plugin-Layer gehoben (Plattform-Konzept, hosts chat/dashboard/window)
- MiniAppDef: permission (fail-closed) + settings_schema + col/row_span + hosts + component + order + builtin
- MiniAppContribution + FrontendDashboardWidget (Manifest-Schema) um M1-Felder erweitert — dashboard_widgets ist Alias von miniapps (ein Contribution-Typ, #359-Philosophie)
- BasePlugin.on_activate: automatische Manifest-Registrierung; on_deactivate: unregister_plugin (nur eigene Apps)
- GET /api/v1/miniapps (server-seitig permission-gefiltert, ?host=) + GET /api/v1/miniapps/{app_id} (403/404 fail-closed)
- kommunikation/miniapp_registry.py = Kompatibilitaets-Bruecke (Bestands-Importer unveraendert)
- Doku: api-documentation.md + plugin-development-guide.md (MiniApp-Beitragsmuster)

TDD: Rot 16 failed -> Gruen 16/16; Regressionen: contracts 23/23, lifecycle+route_order 4/4; ruff clean (M1-Dateien, Vorbestand per Stash bewiesen); create_app OK

app/plugins/manifest.py

@@ -148,6 +148,10 @@ class FrontendDashboardWidget(BaseModel):
     col_span: int = Field(default=1, description="Grid column span (1-4)")
     row_span: int = Field(default=1, description="Grid row span")
     permission: str = Field(default="", description="Optional permission required")
+    settings_schema: dict[str, Any] = Field(
+        default_factory=dict,
+        description="JSON schema for per-instance settings (Phase M1)",
+    )
 
 
 class CustomFieldDefinition(BaseModel):
@@ -173,6 +177,19 @@ class MiniAppContribution(BaseModel):
     icon: str = Field(default="AppWindow")
     description: str = Field(default="")
     render_schema: dict[str, Any] = Field(default_factory=dict)
+    # Phase M1: universal MiniApp fields
+    permission: str = Field(default="", description="Required permission (fail-closed)")
+    settings_schema: dict[str, Any] = Field(
+        default_factory=dict, description="JSON schema for per-instance settings"
+    )
+    col_span: int = Field(default=1, ge=1, le=12, description="Grid column span")
+    row_span: int = Field(default=1, ge=1, le=12, description="Grid row span")
+    hosts: list[str] = Field(
+        default_factory=lambda: ["chat", "dashboard", "window"],
+        description="Hosts this MiniApp may appear in",
+    )
+    component: str = Field(default="", description="Frontend component path")
+    order: int = Field(default=100, description="Sort order in palettes")
 
 
 class PluginManifest(BaseModel):