feat: add NFO scan after rescan and year caching

- Add nfo_scan_after_rescan config option (default: true)
- Implement year caching in AniworldLoader and EnhancedAniWorldLoader
- Make get_year abstract method in base provider
- Run NFO validation/creation after scheduled rescan completes
- Add _YearDict cache to avoid re-extracting year from HTML

tests/unit/test_provider_edge_cases.py

@@ -25,6 +25,7 @@ def _loader() -> AniworldLoader:
     loader = AniworldLoader.__new__(AniworldLoader)
     loader._KeyHTMLDict = {}
     loader._EpisodeHTMLDict = {}
+    loader._YearDict = {}
     loader.ANIWORLD_TO = "https://aniworld.to"
     loader.DEFAULT_REQUEST_TIMEOUT = 10
     loader.session = MagicMock()