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/models/__init__.py

@@ -0,0 +1,9 @@
+"""SQLAlchemy models package."""
+
+from app.models.admin_user import AdminUser
+from app.models.contact import Contact
+from app.models.equipment import EquipmentCache
+from app.models.rental_request import RentalRequest, RentalRequestItem
+from app.models.sync_log import SyncLog
+
+__all__ = ["AdminUser", "Contact", "EquipmentCache", "RentalRequest", "RentalRequestItem", "SyncLog"]