fix(migration): wrap ALTER TYPE ADD VALUE in DO block with IF NOT EXISTS check

services/mam-api/src/db/migrations/034-add-pending-migration-status.sql

@@ -1,2 +1,8 @@
 -- 2026-06: add 'pending_migration' to asset_status enum for manual SMB-to-S3 promotion
-ALTER TYPE asset_status ADD VALUE 'pending_migration';
+DO $$
+BEGIN
+  IF NOT EXISTS (SELECT 1 FROM pg_enum WHERE enumlabel = 'pending_migration' AND enumtypid = 'asset_status'::regtype) THEN
+    ALTER TYPE asset_status ADD VALUE 'pending_migration';
+  END IF;
+END
+$$;