fix: MFA setup completion not updating UI state

Root cause: the MFA status endpoint returned `mfa_enabled` as the JSON
key but the TypeScript MfaStatus interface expected `enabled`. At
runtime, `mfaStatus.value?.enabled` was always `undefined`, so
`isEnabled` was always false — the banner never hid and the method
cards never showed "Geconfigureerd".

Additionally, the auth store had no way to re-fetch /auth/me after
initialization, so `mfaSetupRequired` was never properly refreshed
from the backend after MFA setup.

Fixes:
- Rename `mfa_enabled` → `enabled` in the MFA status endpoint response
  to match the TypeScript type (and the /auth/me MeResource which
  already used `enabled`)
- Add `refreshUser()` to the auth store for post-initialization
  re-fetching of /auth/me
- Call `refreshUser()` in onSetupCompleted so the store reflects the
  backend state without a full page reload
- Update backend tests to match the renamed response key

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

api/app/Http/Controllers/Api/V1/Auth/MfaSetupController.php

@@ -135,7 +135,7 @@ final class MfaSetupController extends Controller
         $user = $request->user();
 
         return $this->success([
-            'mfa_enabled' => $user->mfa_enabled,
+            'enabled' => $user->mfa_enabled,
             'method' => $user->mfa_method,
             'confirmed_at' => $user->mfa_confirmed_at?->toIso8601String(),
             'backup_codes_remaining' => $this->mfaService->getRemainingBackupCodeCount($user),