Add Scramble package and configure API documentation; update letter routes and controller responses

routes/api.php

@@ -28,7 +28,7 @@ Route::get('/user', function (Request $request) {
 })->middleware('auth:sanctum');
 
 // Letter Management Routes
-Route::apiResource('letters', LetterController::class);
+Route::apiResource('letter', LetterController::class);
 
 // File Attachment Routes
 Route::get('/lampiran/{id}', [LetterController::class, 'letterLampiran'])