✨ feat(api): menambahkan controller API untuk ringkasan saldo rekening

- Menambahkan `AccountBalanceController` dengan endpoint `GET /api/balance`.
- Integrasi dengan `AccountBalanceService` untuk pengelolaan logika bisnis.
- Validasi request menggunakan `BalanceSummaryRequest`.
- Formatting response dengan `BalanceSummaryResource`.
- Menyediakan ringkasan saldo, transaksi, dan metadata dengan response JSON konsisten.

routes/api.php

@@ -3,7 +3,13 @@
     use Illuminate\Support\Facades\Route;
     use Modules\Webstatement\Http\Controllers\CustomerController;
     use Modules\Webstatement\Http\Controllers\EmailBlastController;
+    use Modules\Webstatement\Http\Controllers\Api\AccountBalanceController;
 
     Route::post('/email-blast', [EmailBlastController::class, 'sendEmailBlast']);
     Route::get('/email-blast-history', [EmailBlastController::class, 'getEmailBlastHistory']);
     Route::get('/customers/search', [CustomerController::class, 'search']);
+
+    // Account Balance API Routes
+    Route::prefix('balance')->group(function () {
+        Route::get('/', [AccountBalanceController::class, 'getBalanceSummary']);
+    });