feat(billing): renewals, coupons, VAT numbering, billing cycles and invoice payment tracking

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

app/Http/Controllers/Api/Client/BillingProfileController.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace App\Http\Controllers\Api\Client;
+
+use App\Http\Controllers\Controller;
+use App\Http\Requests\Api\BillingProfileRequest;
+use App\Support\CustomerBillingProfile;
+use Illuminate\Http\JsonResponse;
+
+class BillingProfileController extends Controller
+{
+    public function show(): JsonResponse
+    {
+        return response()->json(['error' => false, 'data' => CustomerBillingProfile::payload(auth('client')->user())]);
+    }
+
+    public function update(BillingProfileRequest $request): JsonResponse
+    {
+        return response()->json([
+            'error' => false,
+            'message' => 'Đã lưu thông tin xuất hóa đơn',
+            'data' => CustomerBillingProfile::save(auth('client')->user(), $request->validated()),
+        ]);
+    }
+}