9e3decc91a
- Add timestamp field with auto-population via DateTime.now() - Update all factory constructors to include timestamp - Serialize timestamp as millisecondsSinceEpoch in toMap() - Deserialize with fallback to DateTime.now() in fromMap() - Add timestamp parameter to copyWith() method - Remove const modifiers to allow DateTime.now() runtime values Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>