Make sure we load the backup integration before frontend (#137010)

homeassistant/bootstrap.py

@@ -161,6 +161,10 @@ FRONTEND_INTEGRATIONS = {
     # integrations can be removed and database migration status is
     # visible in frontend
     "frontend",
+    # Backup is an after dependency of frontend, after dependencies
+    # are not promoted from stage 2 to earlier stages, so we need to
+    # add it here.
+    "backup",
 }
 RECORDER_INTEGRATIONS = {
     # Setup after frontend