Problem

No reflog exists. When a ref is updated (branch move, force-push, HEAD change), the previous value is lost. There is no operation history to inspect or recover from.

Impact

• Cannot recover from accidental ref updates
• No audit trail for ref changes
• git reflog equivalent unavailable for debugging

Acceptance Criteria

• Ref updates automatically append to a per-ref log
• Reflog entries include: old SHA, new SHA, actor, timestamp, message
• API to read reflog entries (with pagination)
• API to expire old reflog entries
• Storage behaviour extended for reflog operations
• Works across filesystem and memory backends (S3 optional/best-effort)