fix(settingsmigrator): prevent region migration from running multiple times (#1255)

Adds a guard clause to skip region migration if discoverRegion and
streamingRegion properties already exist in settings. This prevents
accidental overwrites of existing region settings during multiple runs
and ensures the migration only executes when needed.

Previously, the migration would run every time regardless of whether the
new region properties existed, potentially overwriting user preferences.

fix #1251

server/lib/settings/migrations/0004_migrate_region_setting.ts

@@ -1,6 +1,13 @@
 import type { AllSettings } from '@server/lib/settings';
 
 const migrateRegionSetting = (settings: any): AllSettings => {
+  if (
+    settings.main.discoverRegion !== undefined &&
+    settings.main.streamingRegion !== undefined
+  ) {
+    return settings;
+  }
+
   const oldRegion = settings.main.region;
   if (oldRegion) {
     settings.main.discoverRegion = oldRegion;