fix: use wasChanged() instead of isDirty() in updated hooks

Critical Bug Fix:
- isDirty() always returns false in updated() hook
- wasChanged() correctly tracks modifications after save

Files Fixed:
- ServerSetting: Sentinel restart now triggers on config changes
- DeletesUserSessions: Session invalidation now works on password change

Security Impact:
- CRITICAL: Password changes now properly invalidate user sessions
- Prevents session hijacking after password reset

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

app/Models/InstanceSettings.php

@@ -35,7 +35,7 @@ class InstanceSettings extends Model
     protected static function booted(): void
     {
         static::updated(function ($settings) {
-            if ($settings->isDirty('helper_version')) {
+            if ($settings->wasChanged('helper_version')) {
                 Server::chunkById(100, function ($servers) {
                     foreach ($servers as $server) {
                         PullHelperImageJob::dispatch($server);