sync_tags held git2 types (StringArray, Repository) across .await points
on sea-orm DB operations. Applied the same pattern as sync_refs:
- Added collect_tag_refs() sync helper that collects all tag metadata
(name, oid, description, tagger) into owned TagTip structs.
- sync_tags now calls collect_tag_refs() before any .await, so no git2
types cross the async boundary.
- Removed #[allow(dead_code)] from TagTip now that it's consumed.
7a2a3c51c4