feat: add City10 platform with Laravel 13, AI agents, 3D viewer, and LGPD compliance

Initial commit of the complete City10 virtual city simulation platform.

Backend (Laravel 13):
- REST API with Sanctum tokens and session-based web authentication
- Role-based access control (admin/user) with middleware protection
- AI agent CRUD with OpenRouter.ai integration restricted to free models
- Store management with 3D coordinates and AI shopkeeper assignment
- Versioned legal documents (Terms, Privacy, Cookies) with LGPD audit trail
- Math CAPTCHA on public forms and multi-language support (pt_BR, en, es)

Frontend:
- Responsive Blade templates with Tailwind CSS v4
- Three.js 3D city viewer with SSE chat streaming to AI agents
- Admin panel for store and user administration

Infrastructure:
- MariaDB/MySQL database with comprehensive migrations
- Database seeders for demo content and test accounts
- PHPUnit test suite and Laravel Pint code styling
- Vite build configuration with hot reload

app/Http/Middleware/EnsureUserIsAdmin.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace App\Http\Middleware;
+
+use Closure;
+use Illuminate\Http\Request;
+use Symfony\Component\HttpFoundation\Response;
+
+/**
+ * Restricts access to platform administrators.
+ *
+ * Returns 403 for non-admin users, protecting the admin-only endpoints
+ * (user management, agent registry, store registry administration).
+ */
+class EnsureUserIsAdmin
+{
+    /**
+     * Handle an incoming request.
+     *
+     * @param  Closure(Request): (Response)  $next
+     */
+    public function handle(Request $request, Closure $next): Response
+    {
+        $user = $request->user();
+
+        if ($user === null || ! $user->isAdmin()) {
+            if ($request->expectsJson()) {
+                return response()->json(['message' => __('auth.forbidden')], 403);
+            }
+
+            abort(403, __('auth.forbidden'));
+        }
+
+        return $next($request);
+    }
+}