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/LocalFileVolume.php

@@ -14,6 +14,7 @@ class LocalFileVolume extends BaseModel
         // 'mount_path' => 'encrypted',
         'content' => 'encrypted',
         'is_directory' => 'boolean',
+        'is_preview_suffix_enabled' => 'boolean',
     ];
 
     use HasFactory;