feat: add UserResource with is_admin toggle and delete

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/Models/User.php

@@ -14,7 +14,7 @@ use Illuminate\Notifications\Notifiable;
 use Illuminate\Support\Str;
 use Laravel\Fortify\TwoFactorAuthenticatable;
 
-#[Fillable(['name', 'email', 'password'])]
+#[Fillable(['name', 'email', 'password', 'is_admin', 'postcode'])]
 #[Hidden(['password', 'two_factor_secret', 'two_factor_recovery_codes', 'remember_token'])]
 class User extends Authenticatable implements FilamentUser
 {