feat(preview): add configurable PR suffix toggle for volumes

Add `is_preview_suffix_enabled` flag to `local_file_volumes` and
`local_persistent_volumes` tables, allowing per-volume control over
whether a `-pr-N` suffix is appended during preview deployments.

Defaults to `true` to preserve existing behavior. Users can disable
it for volumes containing shared config or repository scripts that
should not be isolated per PR.

app/Models/LocalPersistentVolume.php

@@ -10,6 +10,10 @@ class LocalPersistentVolume extends Model
 {
     protected $guarded = [];
 
+    protected $casts = [
+        'is_preview_suffix_enabled' => 'boolean',
+    ];
+
     public function resource()
     {
         return $this->morphTo('resource');