feat: rescan now saves to database instead of data files

- Update SeriesApp.rescan() to use database storage by default (use_database=True)
- Use SerieScanner.scan_async() for database mode, which saves directly to DB
- Fall back to legacy file-based scan() when use_database=False (for CLI compatibility)
- Reinitialize SerieList from database after scan when in database mode
- Update unit tests to use use_database=False for mocked tests
- Add parameter to control storage mode for backward compatibility

src/core/SeriesApp.py

@@ -457,14 +457,27 @@ class SeriesApp:
 
             return False
 
-    async def rescan(self) -> int:
+    async def rescan(self, use_database: bool = True) -> int:
         """
         Rescan directory for missing episodes (async).
+        
+        When use_database is True (default), scan results are saved to the
+        database instead of data files. This is the preferred mode for the
+        web application.
+
+        Args:
+            use_database: If True, save scan results to database.
+                If False, use legacy file-based storage (deprecated).
 
         Returns:
             Number of series with missing episodes after rescan.
         """
-        logger.info("Starting directory rescan")
+        logger.info(
+            "Starting directory rescan (database mode: %s)",
+            use_database
+        )
+
+        total_to_scan = 0
 
         try:
             # Get total items to scan
@@ -507,12 +520,34 @@ class SeriesApp:
                     )
                 )
 
-            # Perform scan
-            await asyncio.to_thread(self.serie_scanner.scan, scan_callback)
+            # Perform scan - use database mode when available
+            if use_database:
+                # Import here to avoid circular imports and allow CLI usage
+                # without database dependencies
+                from src.server.database.connection import get_db_session
+                
+                async with get_db_session() as db:
+                    await self.serie_scanner.scan_async(db, scan_callback)
+                    logger.info("Scan results saved to database")
+            else:
+                # Legacy file-based mode (deprecated)
+                await asyncio.to_thread(
+                    self.serie_scanner.scan, scan_callback
+                )
 
-            # Reinitialize list
-            self.list = SerieList(self.directory_to_search)
-            await self._init_list()
+            # Reinitialize list from the appropriate source
+            if use_database:
+                from src.server.database.connection import get_db_session
+                
+                async with get_db_session() as db:
+                    self.list = SerieList(
+                        self.directory_to_search, db_session=db
+                    )
+                    await self.list.load_series_from_db(db)
+                    self.series_list = self.list.GetMissingEpisode()
+            else:
+                self.list = SerieList(self.directory_to_search)
+                await self._init_list()
 
             logger.info("Directory rescan completed successfully")
 
@@ -540,7 +575,7 @@ class SeriesApp:
             self._events.scan_status(
                 ScanStatusEventArgs(
                     current=0,
-                    total=total_to_scan if 'total_to_scan' in locals() else 0,
+                    total=total_to_scan,
                     folder="",
                     status="cancelled",
                     message="Scan cancelled by user",
@@ -555,7 +590,7 @@ class SeriesApp:
             self._events.scan_status(
                 ScanStatusEventArgs(
                     current=0,
-                    total=total_to_scan if 'total_to_scan' in locals() else 0,
+                    total=total_to_scan,
                     folder="",
                     status="failed",
                     error=e,