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/conftest.py

@@ -1,5 +1,6 @@
 import os
 from contextlib import asynccontextmanager
+from unittest.mock import AsyncMock, patch
 
 # Set required env vars before importing app
 os.environ.setdefault("SECRET_KEY", "test-secret-key-for-testing-only")
@@ -238,3 +239,16 @@ async def user_no_roles(client_factory):
         "cookies": dict(response.cookies),
         "response": response,
     }
+
+
+@pytest.fixture(autouse=True)
+def mock_enqueue_job():
+    """Mock job enqueueing for all tests.
+
+    pgqueuer requires PostgreSQL-specific features that aren't available
+    in the test database setup. We mock the enqueue function to avoid
+    connection issues while still testing the counter logic.
+    """
+    mock = AsyncMock(return_value=1)  # Return a fake job ID
+    with patch("routes.counter.enqueue_random_number_job", mock):
+        yield mock