fix(db): make 0004 migration no-op

Author: onmax

server/db/migrations/0004_add_validator_is_listed.sql

@@ -1 +1,4 @@
-ALTER TABLE `validators` ADD `is_listed` integer;
+-- The `is_listed` column was added manually in remote D1 databases.
+-- Keep this as a no-op migration so deploy-time migrations don't fail
+-- with "duplicate column name: is_listed".
+SELECT 1;