feat(purchase): implement PurchaseController with CRUD operations and request validation

app/Domains/Purchase/Requests/StorePurchaseRequest.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace App\Domains\Purchase\Requests;
+
+use Illuminate\Foundation\Http\FormRequest;
+use Illuminate\Validation\Rule;
+
+class StorePurchaseRequest extends FormRequest
+{
+    public function authorize(): bool
+    {
+        return $this->user() !== null;
+    }
+
+    /**
+     * @return array<string, mixed>
+     */
+    public function rules(): array
+    {
+        return [
+            'status' => ['sometimes', 'string', Rule::in(['pending', 'paid', 'cancelled'])],
+            'payment_status' => ['sometimes', 'string', Rule::in(['pending', 'approved', 'rejected'])],
+            'payment_method' => ['nullable', 'string', 'max:255'],
+            'items' => ['required', 'array', 'min:1'],
+            'items.*.producto_variante_id' => ['required', 'integer', 'exists:productos_variantes,id'],
+            'items.*.cantidad' => ['required', 'integer', 'min:1'],
+        ];
+    }
+}