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

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

app/Models/CouponRedemption.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+class CouponRedemption extends Model
+{
+    protected $guarded = [];
+
+    protected $casts = [
+        'amount' => 'integer',
+        'released_at' => 'datetime',
+    ];
+
+    public function coupon(): BelongsTo
+    {
+        return $this->belongsTo(Coupon::class);
+    }
+
+    public function customer(): BelongsTo
+    {
+        return $this->belongsTo(Customer::class);
+    }
+
+    public function order(): BelongsTo
+    {
+        return $this->belongsTo(Order::class);
+    }
+}