- Added `DirectoryManager` utility for consistent directory operations.
- Introduced directory name sanitization and uniqueness enforcement for `TravelDiary`.
- Updated `TravelDiaryService` with enhanced creation, update, and deletion workflows, including filesystem management.
- Improved `PhotoService` to hash files, copy photos to specific diary directories, and manage updates safely.
- Refined error handling and cascaded changes across related entities (e.g., `Entry` relationships).