feat: T03 backend core – FastAPI + DB models + Equipment API + Redis cache + health + tests

- FastAPI app with CORS, lifespan handlers
- Pydantic Settings config (DB, Redis, CORS, SMTP, JWT, Rentman)
- SQLAlchemy async engine + session (DeclarativeBase)
- 6 DB models: EquipmentCache, RentalRequest, RentalRequestItem, Contact, AdminUser, SyncLog
- Pydantic schemas: EquipmentItem, EquipmentDetail, PaginatedEquipment, ContactCreate, ContactResponse
- Redis cache helper: set/get/delete_pattern, rate limiting, equipment key builders
- Equipment router: list (search/category/sort/pagination), detail, categories – all cached
- Contact router: POST with Pydantic validation + rate limiting (5/min)
- Health router: GET /api/health with DB + Redis status
- 28 pytest tests (all pass, 90% coverage)
- Dockerfile, requirements.txt, pytest.ini, test_report.md

backend/app/routers/contact.py

@@ -0,0 +1,39 @@
+"""Contact form endpoint with rate limiting."""
+
+from fastapi import APIRouter, Depends, HTTPException, Request, status
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.cache import check_rate_limit
+from app.database import get_db
+from app.models.contact import Contact
+from app.schemas.contact import ContactCreate, ContactResponse
+
+router = APIRouter(prefix="/contact", tags=["contact"])
+
+
+@router.post("", response_model=ContactResponse, status_code=status.HTTP_201_CREATED)
+async def create_contact(
+    payload: ContactCreate,
+    request: Request,
+    db: AsyncSession = Depends(get_db),
+) -> ContactResponse:
+    """Submit a contact form message with rate limiting."""
+    client_ip = request.client.host if request.client else "unknown"
+    allowed = await check_rate_limit(f"contact:{client_ip}", max_requests=5, window=60)
+    if not allowed:
+        raise HTTPException(
+            status_code=status.HTTP_429_TOO_MANY_REQUESTS,
+            detail="Rate limit exceeded. Please try again later.",
+        )
+
+    contact = Contact(
+        name=payload.name,
+        email=str(payload.email),
+        phone=payload.phone,
+        message=payload.message,
+        privacy_consent=payload.privacy_consent,
+    )
+    db.add(contact)
+    await db.commit()
+
+    return ContactResponse(success=True, message="Kontakt-Anfrage erfolgreich gesendet.")