genres had only case-sensitive name UNIQUE while authors/tags use
UNIQUE (lower(name)); sync_genres could race two case variants into duplicate
rows (audit DB-3). Migration 0038 pre-dedups then adds
UNIQUE (lower(name)); sync_genres upserts ON CONFLICT (lower(name)). Tested.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
