Implement MarkNotificationSent, IsNotificationSent, and
GetUnnotifiedReleases with LEFT JOIN query. Includes 10
table-driven tests covering success, error, idempotent,
and edge cases. Also go fmt cleanup on existing files.
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>
