feat(checkout): track current cart purchase

database/migrations/2026_08_21_010000_add_current_purchase_id_to_carts_table.php

@@ -0,0 +1,46 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::table('carritos', function (Blueprint $table): void {
+            $table->foreignId('current_purchase_id')
+                ->nullable()
+                ->after('origin')
+                ->constrained('compras')
+                ->nullOnDelete();
+            $table->unique('current_purchase_id', 'carts_current_purchase_unique');
+        });
+
+        DB::table('carritos')
+            ->select('id')
+            ->orderBy('id')
+            ->each(function (object $cart): void {
+                $purchaseId = DB::table('compras')
+                    ->where('cart_id', $cart->id)
+                    ->whereIn('status', ['created', 'pending_payment'])
+                    ->latest('id')
+                    ->value('id');
+
+                if ($purchaseId !== null) {
+                    DB::table('carritos')
+                        ->where('id', $cart->id)
+                        ->update(['current_purchase_id' => $purchaseId]);
+                }
+            });
+    }
+
+    public function down(): void
+    {
+        Schema::table('carritos', function (Blueprint $table): void {
+            $table->dropUnique('carts_current_purchase_unique');
+            $table->dropConstrainedForeignId('current_purchase_id');
+        });
+    }
+};