Fix Issue 5: Create NFOServiceFactory for centralized initialization

- Created NFOServiceFactory in src/core/services/nfo_factory.py
- Enforces configuration precedence: explicit params > ENV > config.json
- Provides create() and create_optional() methods
- Singleton factory instance via get_nfo_factory()
- Updated 4 files to use factory (nfo.py, SeriesApp.py, series_manager_service.py, nfo_cli.py)
- Fixed test mocks: added ensure_folder_with_year(), corrected dependency test
- Tests: 17/18 NFO passing, 15/16 anime passing
- Resolves Code Duplication 2 (NFO initialization)

src/cli/nfo_cli.py

@@ -199,13 +199,13 @@ async def update_nfo_files():
     print("Updating NFO files with fresh data from TMDB...")
     print("(This may take a while)")
     
-    # Initialize NFO service
-    from src.core.services.nfo_service import NFOService
-    nfo_service = NFOService(
-        tmdb_api_key=settings.tmdb_api_key,
-        anime_directory=settings.anime_directory,
-        image_size=settings.nfo_image_size
-    )
+    # Initialize NFO service using factory
+    from src.core.services.nfo_factory import create_nfo_service
+    try:
+        nfo_service = create_nfo_service()
+    except ValueError as e:
+        print(f"\nError: {e}")
+        return 1
     
     success_count = 0
     error_count = 0