Phase 2: Job enqueueing from counter

- Add backend/jobs.py with enqueue_random_number_job function
- Modify counter increment endpoint to enqueue job after incrementing
- Add mock_enqueue_job fixture to conftest.py for all tests
- Add test_increment_enqueues_job_with_user_id to verify correct user_id
- Job is enqueued synchronously; failure causes request to fail

backend/tests/test_counter.py

@@ -11,6 +11,38 @@ from tests.conftest import create_user_with_roles
 from tests.helpers import create_invite_for_godfather, unique_email
 
 
+@pytest.mark.asyncio
+async def test_increment_enqueues_job_with_user_id(client_factory, mock_enqueue_job):
+    """Verify that incrementing the counter enqueues a job with the user's ID."""
+    async with client_factory.get_db_session() as db:
+        godfather = await create_user_with_roles(
+            db, unique_email("gf"), "pass123", [ROLE_REGULAR]
+        )
+        invite_code = await create_invite_for_godfather(db, godfather.id)
+
+    reg = await client_factory.post(
+        "/api/auth/register",
+        json={
+            "email": unique_email(),
+            "password": "testpass123",
+            "invite_identifier": invite_code,
+        },
+    )
+    cookies = dict(reg.cookies)
+
+    # Get user ID from the me endpoint
+    async with client_factory.create(cookies=cookies) as authed:
+        me_response = await authed.get("/api/auth/me")
+        user_id = me_response.json()["id"]
+
+        # Increment counter
+        response = await authed.post("/api/counter/increment")
+        assert response.status_code == 200
+
+    # Verify enqueue was called with the correct user_id
+    mock_enqueue_job.assert_called_once_with(user_id)
+
+
 # Protected endpoint tests - without auth
 @pytest.mark.asyncio
 async def test_get_counter_requires_auth(client):