M1: implement operational core

Demo auth, seed import/reset, dashboard, vehicle/booking list+detail, audit trail. Backend: 19 tests passing, ruff clean. Frontend: React Router shell, typed API client, responsive pages. Verified end-to-end via curl and browser.

backend/app/cli.py

@@ -0,0 +1,35 @@
+from __future__ import annotations
+
+import argparse
+
+from app.core.db import SessionLocal
+from app.seed_loader import reset_and_seed
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(prog="app.cli")
+    subparsers = parser.add_subparsers(dest="command", required=True)
+
+    seed_parser = subparsers.add_parser("seed", help="Load the deterministic demo dataset")
+    seed_parser.add_argument(
+        "--reset", action="store_true", help="Clear existing data before loading"
+    )
+
+    args = parser.parse_args()
+
+    if args.command == "seed":
+        if not args.reset:
+            raise SystemExit(
+                "Only 'seed --reset' is supported: seeding always rebuilds the demo dataset."
+            )
+        db = SessionLocal()
+        try:
+            result = reset_and_seed(db)
+            for name, count in result.counts.items():
+                print(f"{name}: {count}")
+        finally:
+            db.close()
+
+
+if __name__ == "__main__":
+    main()