Initial commit: Rentman Clone - Phase 0-6 (T001-T023)

Completed:
- Phase 0: Project Setup (T001-T003) - Docker Compose, FastAPI skeleton, React SPA
- Phase 1: Auth System (T004-T008) - DB models, JWT auth, RBAC middleware, user management
- Phase 2: Contacts & Tags (T009-T011) - CRUD API + UI
- Phase 3: Equipment Catalog (T012-T014) - Models, API, UI with barcode/QR
- Phase 4: Crew Management (T015-T017) - Models, availability, UI
- Phase 5: Vehicle Fleet (T018-T020) - Models, assignments, UI
- Phase 6: Projects (T021-T023) - Project hierarchy models, CRUD API, list/detail UI

backend/app/db/session.py

@@ -0,0 +1,31 @@
+"""Async SQLAlchemy engine and session factory."""
+
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
+from sqlalchemy.pool import NullPool
+
+from app.core.config import settings
+
+engine = create_async_engine(
+    settings.DATABASE_URL,
+    echo=settings.APP_DEBUG,
+    poolclass=NullPool,  # SQLite doesn't support connection pooling across threads
+)
+
+AsyncSessionFactory = async_sessionmaker(
+    engine,
+    class_=AsyncSession,
+    expire_on_commit=False,
+)
+
+
+async def get_async_session() -> AsyncSession:
+    """Dependency that provides an async database session."""
+    async with AsyncSessionFactory() as session:
+        try:
+            yield session
+            await session.commit()
+        except Exception:
+            await session.rollback()
+            raise
+        finally:
+            await session.close()