Preserve the guide until a complete EPG refresh can activate

Adapted from MikaelKW/nodecast-tv-plus commits c267d98d734753a09b08d267c8ec2c3fa11c33f5, b761690bac7626a3cc5ddf754d96b14a02f506fe, and 5524fdaffed5c6a44ae69474e7eaa2f18d428c75. Preserve every parser batch, decode gzip once, and retain live channel metadata.

Co-authored-by: Mikael <mikaelkwessel@gmail.com>

server/routes/sources.js

@@ -120,6 +120,7 @@ router.delete('/:id', async (req, res) => {
         }
 
         // Cascade delete: Clean up SQLite data for this source
+        syncService.invalidateEpgSource(sourceId);
         const db = getDb();
         const deleteCategories = db.prepare('DELETE FROM categories WHERE source_id = ?');
         const deleteItems = db.prepare('DELETE FROM playlist_items WHERE source_id = ?');