fix: use fs/promises for settings (#1057)

* fix: use fs/promises for settings

This PR switches from synchronous operations with the 'fs' module to asynchronous operations with
the 'fs/promises' module. It also corrects a small error with hostname migration.

* fix: add missing merge function of default and current config

* refactor: add more logs to migration

server/routes/auth.ts

@@ -87,7 +87,7 @@ authRoutes.post('/plex', async (req, res, next) => {
       });
 
       settings.main.mediaServerType = MediaServerType.PLEX;
-      settings.save();
+      await settings.save();
       startJobs();
 
       await userRepository.save(user);
@@ -366,7 +366,7 @@ authRoutes.post('/jellyfin', async (req, res, next) => {
       settings.jellyfin.urlBase = body.urlBase ?? '';
       settings.jellyfin.useSsl = body.useSsl ?? false;
       settings.jellyfin.apiKey = apiKey;
-      settings.save();
+      await settings.save();
       startJobs();
 
       await userRepository.save(user);