Content state machine + scheduled publisher + GC jobs

[tayebmokni]

Summary

Implement the content-state machine for posts. Enforce allowed transitions, fire post.transitioned hooks, and integrate the scheduled publisher (Asynq job that scans WHERE status='scheduled' AND publish_at <= now() every 30s).

Design reference

• docs/01-core-cms.md §5 (Content States)
• docs/01-core-cms.md §5.2 (State machine diagram)
• docs/01-core-cms.md §5.3 (Implementation — Go-side validation, scheduler)

Acceptance criteria

• internal/content/states.go defines AllowedTransition(from, to Status) bool matching §5.2
• Repository's Transition(ctx, id, to, by) validates the transition before UPDATE
• On every successful transition, a post.transitioned hook fires with {from, to, post_id, user_id} payload
• Term counts update on transitions affecting public visibility (draft→published increments terms.count for attached terms)
• Asynq cron job runs every 30s, batches eligible scheduled posts, transitions to published
• Auto-draft GC job: removes auto-draft posts older than 24h
• Trash GC job: purges trash posts older than 30 days
• Integration tests cover every legal transition and reject every illegal one

Dependencies

#22, #24

Complexity

M

[tayebmokni]

Closing — shipped in the final-wave PR (#487-#492). Auto-close only fires for first ref.