Unlike JOB_RANDOM_NUMBER which is used for external job enqueueing,
JOB_FETCH_BITCOIN_PRICE is only used internally by the scheduler.
Move it to worker.py to clarify it's not part of the public job API.
- Added ASYNCPG_DATABASE_URL constant in database.py
- Updated jobs.py to import from database module
- Updated worker.py to import from database module
- Removed duplicate URL parsing logic from both files
- Added get_job_pool() for lazy pool initialization
- Added close_job_pool() for graceful shutdown
- Hooked pool shutdown into FastAPI lifespan
- Reuses connections instead of creating new ones per enqueue
- 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
