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_monitored_provider.py

@@ -53,6 +53,9 @@ class MockProvider(Loader):
     def get_title(self, key):
         return self._title
 
+    def get_year(self, key) -> int | None:
+        return 2024
+
     def get_season_episode_count(self, slug):
         return self._season_episodes
 
@@ -66,6 +69,9 @@ class ConcreteMonitoredWrapper(MonitoredProviderWrapper):
     def unsubscribe_download_progress(self, handler):
         pass
 
+    def get_year(self, key: str) -> int | None:
+        return None
+
 
 @pytest.fixture
 def mock_provider():