feat(server): wire audit trail (submission, vote, watcher) via admin_audit_log_write

[flyingrobots]

Summary

Persist administrative audit entries for key actions using admin_audit_log_write().

Acceptance Criteria

• /rpc/submission.create writes audit row
• /rpc/vote.continue writes audit row
• watcher flips write audit row

Notes/Links

• db/rpc.sql (admin_audit_log_write)