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

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

app/Http/Requests/Api/Order/CouponPreviewRequest.php

@@ -0,0 +1,27 @@
+<?php
+
+namespace App\Http\Requests\Api\Order;
+
+use App\Support\BillingCycleCatalog;
+use Illuminate\Foundation\Http\FormRequest;
+use Illuminate\Validation\Rule;
+
+class CouponPreviewRequest extends FormRequest
+{
+    public function authorize(): bool
+    {
+        return true;
+    }
+
+    public function rules(): array
+    {
+        return [
+            'coupon_code' => ['required', 'string', 'max:50'],
+            'product_id' => ['required', Rule::exists('products', 'uuid')->whereNull('deleted_at')],
+            'billing_cycle' => ['required', Rule::in([...BillingCycleCatalog::codes(), 'onetime'])],
+            'addons' => 'array',
+            'addons.*.addon_id' => 'nullable|exists:product_addon,id',
+            'addons.*.qty' => 'nullable|integer|min:0|max:1000000',
+        ];
+    }
+}