Add migration to add description column to user_storage table

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

db.py

@@ -170,6 +170,12 @@ DO $$ BEGIN
     ALTER TABLE assets ADD COLUMN source_type VARCHAR(50);
 EXCEPTION WHEN duplicate_column THEN NULL;
 END $$;
+
+-- Add description column to user_storage if it doesn't exist
+DO $$ BEGIN
+    ALTER TABLE user_storage ADD COLUMN description TEXT;
+EXCEPTION WHEN duplicate_column THEN NULL;
+END $$;
 """