fix: disable global API key middleware and add test miner creation endpoint

API Key Middleware Changes:
- Disabled global API key middleware in favor of dependency injection
- Added comment explaining the change
- Preserves existing middleware code for reference

Admin Router Enhancements:
✅ NEW ENDPOINT: POST /debug/create-test-miner for debugging marketplace sync
- Creates test miner with id "debug-test-miner"
- Updates existing miner to ONLINE status if already exists
- Returns miner_id and session_token for testing
- Requires

systemd/aitbc-coordinator-api.service

@@ -7,6 +7,7 @@ Type=simple
 User=root
 WorkingDirectory=/opt/aitbc/apps/coordinator-api/src
 Environment=PYTHONPATH=/opt/aitbc/apps/coordinator-api/src:/opt/aitbc/packages/py/aitbc-sdk/src:/opt/aitbc/packages/py/aitbc-crypto/src
+Environment=COORDINATOR_API_KEY=admin_prod_key_use_real_value
 ExecStart=/opt/aitbc/venv/bin/python -m uvicorn app.main:app --host 0.0.0.0 --port 8000
 Restart=always
 RestartSec=5