- Add pgCorrectedModerationsTable to shared schema
- Create backend corrections module (stats, list, create endpoints)
- Add TunerPanel with Stats, History, and Submit sub-tabs
- Add AuthOverlay gate for Tuner (admin-only, same as Live)
- Set messages as default tab
- Wire Tuner into sidebar, header, and mobile tab bar
Co-Authored-By: Claude <noreply@anthropic.com>