refactor: move backend in apps/backend

apps/backend/bootstrap/app.php

@@ -0,0 +1,23 @@
+<?php
+
+use Illuminate\Foundation\Application;
+use Illuminate\Foundation\Configuration\Exceptions;
+use Illuminate\Foundation\Configuration\Middleware;
+
+return Application::configure(basePath: dirname(__DIR__))
+    ->withRouting(
+        web: __DIR__ . '/../routes/web.php',
+        api: __DIR__.'/../routes/api.php',
+        commands: __DIR__.'/../routes/console.php',
+        channels: __DIR__.'/../routes/channels.php',
+        health: '/up',
+    )
+    ->withMiddleware(function (Middleware $middleware): void {
+        $middleware->statefulApi();
+        $middleware->validateCsrfTokens(except: [
+            'broadcasting/auth',
+        ]);
+    })
+    ->withExceptions(function (Exceptions $exceptions): void {
+        //
+    })->create();