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

Critical Bug Fix:
- isDirty() always returns false in the updated() hook
- Changes are already persisted when updated() runs
- wasChanged() correctly tracks what was modified during save

Affected Code:
- helper_version check: Now properly triggers PullHelperImageJob
- fqdn check: Now properly clears TrustHosts cache

Impact:
✅ Cache invalidation now works when FQDN changes
✅ Helper image updates now trigger correctly
✅ Security fix cache is properly cleared on config changes

This also fixes an existing bug where helper_version updates
never triggered the PullHelperImageJob dispatch.

🤖 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);
@@ -44,7 +44,7 @@ class InstanceSettings extends Model
             }
 
             // Clear trusted hosts cache when FQDN changes
-            if ($settings->isDirty('fqdn')) {
+            if ($settings->wasChanged('fqdn')) {
                 \Cache::forget('instance_settings_fqdn_host');
             }
         });