Features:
- Resizable printer cards (S/M/L/XL) with toolbar controls on Printers page
- Queue Only mode for staging prints without automatic scheduling
- "Queue Only" option in add/edit queue modals
- Purple "Staged" badge and Play button to release to queue
- manual_start field in database with migration
Fixes:
- Improved camera stream stuck detection with automatic reconnection
Tests:
- Added 16 integration tests for print queue API endpoints
