feat: Implement gallery item sorting and update functionality
- Added `updateGallerySortOrder` method in `ApiService` to update the sort order of gallery items.
- Introduced `GalleryItem` model to represent individual items in a gallery.
- Updated `GalleryCache` provider to handle reordering of gallery items and syncing with the backend.
- Modified `GallerySortOrderSheet` to pass context during reorder completion.
- Enhanced `ProfileWithGalleries` model to include favorite galleries.
- Refactored `ProfilePage` to directly use favorite galleries from the profile state.
- Updated JSON serialization for new fields in models.
- Improved error handling and state management in various components.