Implemented directory management and improved TravelDiary and Photo handling logic.

- 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).

src/pilgrim/utils/__init__.py

@@ -0,0 +1,3 @@
+from .directory_manager import DirectoryManager
+
+__all__ = ['DirectoryManager']