feat(T02): vehicle management + mobile.de push + vehicle UI

- Vehicle model: 25+ fields, 5 vehicle types, soft-delete
- Vehicle CRUD: 7 API endpoints with JWT auth, filter/sort/paginate
- mobile.de: push/update/delete listings, field mapping, retry logic
- MobileDeListing model for sync status tracking
- Frontend: VehicleList, VehicleForm, VehicleDetail, MobileDeStatus
- 73 backend tests (82% coverage), 16 frontend tests

backend/app/main.py

@@ -9,7 +9,7 @@ from fastapi import APIRouter, FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 
 from app.config import settings
-from app.routers import auth, users
+from app.routers import auth, users, vehicles
 
 
 @asynccontextmanager
@@ -40,6 +40,7 @@ app.add_middleware(
 api_v1_router = APIRouter(prefix="/api/v1")
 api_v1_router.include_router(auth.router)
 api_v1_router.include_router(users.router)
+api_v1_router.include_router(vehicles.router)
 
 # Health endpoint (no auth required)
 @api_v1_router.get("/health", tags=["health"])