M0: implement operational core

Backend: SQLAlchemy models, Alembic migrations, requirements lockfile. Frontend: pinned deps, package-lock, vite-env types fix. Verified compose build/health, pytest, ruff clean.

backend/app/models/__init__.py

@@ -0,0 +1,23 @@
+from app.core.db import Base
+from app.models.audit import AuditEvent
+from app.models.booking import Booking
+from app.models.customer import Customer
+from app.models.data_quality import DataQualityIssue
+from app.models.inspection import Inspection
+from app.models.maintenance import MaintenanceRecord
+from app.models.outbox import OutboxEvent
+from app.models.user import User
+from app.models.vehicle import Vehicle
+
+__all__ = [
+    "Base",
+    "AuditEvent",
+    "Booking",
+    "Customer",
+    "DataQualityIssue",
+    "Inspection",
+    "MaintenanceRecord",
+    "OutboxEvent",
+    "User",
+    "Vehicle",
+]