feat: add domain registration form and email notifications

- Create a new Blade view for domain registration (`registrant-tochuc.blade.php`) to capture organization and manager details.
- Implement email templates for new domain orders for both admin (`domain-order-new.blade.php`) and customers (`domain-order-received.blade.php`).
- Add CSV exports for client and domain data.
- Introduce tests for customer mass assignment, password reset, login throttling, and permission gating.
- Ensure service renewals use current pricing and validate ownership for virtual machines.
- Validate mass assignment behavior in service model.

tests/Unit/ServiceFillableTest.php

@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\Unit;
+
+use App\Models\Customer;
+use App\Models\Service;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Tests\TestCase;
+
+class ServiceFillableTest extends TestCase
+{
+    use RefreshDatabase;
+
+    public function test_service_ignores_fields_not_declared_in_fillable(): void
+    {
+        $customer = Customer::factory()->create();
+
+        $service = Service::create([
+            'customer_id' => $customer->id,
+            'server_name' => 'test-server',
+            'status'      => 'active',
+            // Không nằm trong $fillable — không được set qua mass-assignment.
+            'legacy_id'   => 999999,
+        ]);
+
+        $this->assertSame('test-server', $service->server_name);
+        $this->assertNull($service->legacy_id);
+    }
+}