feat(restarts): make resource restart limits opt-in

Default restart limits to zero for applications, previews, and services, and bump the Coolify version to 4.3.21.

app/Models/Application.php

@@ -135,6 +135,10 @@ class Application extends BaseModel
 
     private static $parserVersion = '5';
 
+    protected $attributes = [
+        'max_restart_count' => 0,
+    ];
+
     protected $fillable = [
         'name',
         'description',