fix: conform moved code to eslint indent/quotes, 4-arg mutation callbacks

- eslint --fix on branch-changed backend files (indent shift from the
  module-wrapper nesting in decomposed files); backend lint now 904
  errors vs 1,315 on main
- useMutationWithToast forwards all four TanStack v5 callback args
  (tsc -b strict build flagged the 3-arg passthrough)

backend/src/services/backupService.js

@@ -1177,7 +1177,7 @@ async function runBackupInternal(isManual = false) {
 
 async function startBackupService() {
   try {
-  const config = await resolveConfigWithFallback();
+    const config = await resolveConfigWithFallback();
     if (!config || !normalizeBoolean(config.backup_enabled)) {
       if (backupJob) {
         backupJob.stop();