Docs: Update all documentation for series loading and episode tracking fixes

docs/instructions.md

@@ -120,3 +120,9 @@ For each task completed:
 ## TODO List:
 
 1. ✅ **COMPLETED**: SeriesApp no longer loads series from data files on every startup. Series are now loaded once during setup via `sync_series_from_data_files()` in the FastAPI lifespan. The `SeriesApp` initializes with `skip_load=True` passed to `SerieList`, preventing automatic file loading. Subsequent operations load series from the database through the service layer.
+
+2. ✅ **COMPLETED**: Fixed series visibility and episode tracking:
+   - Series from database are now loaded into SeriesApp's in-memory cache on startup
+   - Missing episodes are saved to database when adding new series
+   - Rescan process properly updates episodes in database (adds new, removes downloaded)
+   - Database stays in sync with filesystem state