- Added useDraftAutosave hook to handle automatic saving of post drafts.
- Enhanced PostEditor component to include a preview tab that fetches and displays rendered markdown.
- Updated Post model to manage draft state and associated published_at timestamp.
- Introduced card_photo association to Post for representing a primary image.
- Modified post form to support draft saving and publishing actions.
- Updated navigation to include links to drafts.
- Added tests for draft saving, preview functionality, and card photo validation.
- Created migrations for new database fields related to drafts and card photos.