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/tests/conftest.py

@@ -0,0 +1,38 @@
+import pytest
+from fastapi.testclient import TestClient
+
+from app.core.db import Base, SessionLocal, engine
+from app.main import app
+from app.seed_loader import reset_and_seed
+
+
+@pytest.fixture(scope="session", autouse=True)
+def _seeded_database():
+    Base.metadata.create_all(engine)
+    db = SessionLocal()
+    try:
+        reset_and_seed(db)
+    finally:
+        db.close()
+    yield
+
+
+@pytest.fixture
+def client() -> TestClient:
+    return TestClient(app)
+
+
+def login(client: TestClient, role: str) -> TestClient:
+    response = client.post("/api/v1/demo/login", json={"role": role})
+    assert response.status_code == 200
+    return client
+
+
+@pytest.fixture
+def ops_client(client: TestClient) -> TestClient:
+    return login(client, "operations_manager")
+
+
+@pytest.fixture
+def employee_client(client: TestClient) -> TestClient:
+    return login(client, "rental_employee")