Fix get_optional_database_session to handle uninitialized database

- Moved RuntimeError catch to encompass get_db_session() call
- Previously only caught during import, not during execution
- Now properly yields None when database not initialized
- Fixes test_add_series_endpoint_authenticated test failure

docs/instructions.md

@@ -297,15 +297,15 @@ For each task completed:
 - **What**: Checking for poster.jpg, logo.png, fanart.jpg existence
 - **Fix**: ✅ Created `src/server/utils/media.py` utility module
 - **Status**: COMPLETED (January 24, 2026)
-- **Resolution**: 
-  - Created comprehensive media utilities module with functions:
-    - `check_media_files()`: Check existence of standard media files
-    - `get_media_file_paths()`: Get paths to existing media files
-    - `has_all_images()`: Check for complete image set
-    - `count_video_files()` / `has_video_files()`: Video file utilities
-  - Constants: `POSTER_FILENAME`, `LOGO_FILENAME`, `FANART_FILENAME`, `NFO_FILENAME`, `VIDEO_EXTENSIONS`
-  - Updated 7 duplicate locations in `nfo.py` and `background_loader_service.py`
-  - Functions accept both `str` and `Path` for compatibility
+- **Resolution**:
+    - Created comprehensive media utilities module with functions:
+        - `check_media_files()`: Check existence of standard media files
+        - `get_media_file_paths()`: Get paths to existing media files
+        - `has_all_images()`: Check for complete image set
+        - `count_video_files()` / `has_video_files()`: Video file utilities
+    - Constants: `POSTER_FILENAME`, `LOGO_FILENAME`, `FANART_FILENAME`, `NFO_FILENAME`, `VIDEO_EXTENSIONS`
+    - Updated 7 duplicate locations in `nfo.py` and `background_loader_service.py`
+    - Functions accept both `str` and `Path` for compatibility
 
 ### Further Considerations (Require Architecture Decisions)