fix(api): hide sensitive fields by default

Add model-level hidden fields for secrets, tokens, keys, notification
credentials, deployment logs, and environment values. Allow explicit
read:sensitive API access to reveal gated private keys and deployment logs,
and cover the behavior with feature and unit tests.

app/Models/CloudInitScript.php

@@ -12,6 +12,10 @@ class CloudInitScript extends Model
         'script',
     ];
 
+    protected $hidden = [
+        'script',
+    ];
+
     protected function casts(): array
     {
         return [