fix(backend): add composite index on user_sources

Add (user_id, enabled) index for the enabled() query path.

Co-authored-by: Ona <no-reply@ona.com>

apps/aelis-backend/drizzle/meta/_journal.json

@@ -8,6 +8,13 @@
       "when": 1773620066366,
       "tag": "0000_wakeful_scorpion",
       "breakpoints": true
+    },
+    {
+      "idx": 1,
+      "version": "7",
+      "when": 1773624297794,
+      "tag": "0001_misty_white_tiger",
+      "breakpoints": true
     }
   ]
 }