Fix SQL syntax error in pg_cron.schedule() calls

Replace dollar-quoted strings with simple single-quoted strings in cron.schedule()
function calls. The cron.schedule() function expects text literals, not dollar-quoted
blocks. Use quote_literal() for the interval value in the cleanup query to properly
escape the string.

supabase/migrations/20260321_extend_scheduled_notifications.sql

@@ -490,22 +490,21 @@ BEGIN
   PERFORM cron.schedule(
     'notification_enqueue_every_min',
     '*/1 * * * *',
-    $$SELECT public.enqueue_all_notifications();$$
+    'SELECT public.enqueue_all_notifications();'
   );
 
   -- Job 2: Process notification queue via pg_net every minute
   PERFORM cron.schedule(
     'notification_process_every_min',
     '*/1 * * * *',
-    $$SELECT public.process_notification_queue();$$
+    'SELECT public.process_notification_queue();'
   );
 
   -- Job 3: Daily cleanup of old processed notifications
   PERFORM cron.schedule(
     'cleanup_old_notifications',
     '0 3 * * *',
-    $$DELETE FROM scheduled_notifications WHERE processed = true AND processed_at < now() - interval '7 days';
+    'DELETE FROM scheduled_notifications WHERE processed = true AND processed_at < now() - interval ' || quote_literal('7 days') || '; DELETE FROM notification_pushes WHERE pushed_at < now() - interval ' || quote_literal('7 days') || ';'
-      DELETE FROM notification_pushes WHERE pushed_at < now() - interval '7 days';$$
   );
 
 EXCEPTION WHEN others THEN