AllowlistService: accept (apply ml_accepted + add to allowlist + clear
rejection; returns whether newly-added so API can kick retro-apply),
add_alias_and_accept, dismiss, reject_applied_tag (remove + record
rejection so the allowlist won't re-apply), threshold update, remove,
list_all.
TagService.rename: refuses on (name, kind, fandom_id) collision with a
message pointing at FC-2c merge. Tests marked integration.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
