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/core/SeriesApp.py

@@ -175,14 +175,11 @@ class SeriesApp:
         self.nfo_service: Optional[NFOService] = None
         if settings.tmdb_api_key:
             try:
-                self.nfo_service = NFOService(
-                    tmdb_api_key=settings.tmdb_api_key,
-                    anime_directory=directory_to_search,
-                    image_size=settings.nfo_image_size,
-                    auto_create=settings.nfo_auto_create
-                )
+                from src.core.services.nfo_factory import get_nfo_factory
+                factory = get_nfo_factory()
+                self.nfo_service = factory.create()
                 logger.info("NFO service initialized successfully")
-            except Exception as e:  # pylint: disable=broad-except
+            except (ValueError, Exception) as e:  # pylint: disable=broad-except
                 logger.warning(
                     "Failed to initialize NFO service: %s", str(e)
                 )