- Fix notifications_sent schema: change to composite PK (rgid, sent_at) per plan spec, remove FK constraint
- Change MarkNotificationSent from INSERT OR REPLACE to INSERT (composite PK semantics)
- Update test: replace idempotent test with duplicate-second and different-time tests
- Refactor UpdateArtistSettings to use switch-based column validation instead of fmt.Sprintf with map lookup
- Remove generated coverage.out from repo, add to .gitignore
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Implements GetArtistSettings, SaveArtistSettings, GetAllArtistSettings,
and UpdateArtistSettings with full test coverage (10 new tests).
All 17 database tests pass.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
