Improve static analysis by adding type hints for $app in artisan and public/index.php (#6531)

* feat: add type hints for $app in artisan and public/index.php

Added PHPDoc type hints for the $app variable to improve static analysis
support in PHPStan and PHPStorm. This prevents tools from incorrectly
flagging the variable and enhances developer experience.

No functional changes; only improves code readability and IDE support.

* Update artisan

* Update index.php

---------

Co-authored-by: Taylor Otwell <taylor@laravel.com>

public/index.php

@@ -1,5 +1,6 @@
 <?php
 
+use Illuminate\Foundation\Application;
 use Illuminate\Http\Request;
 
 define('LARAVEL_START', microtime(true));
@@ -13,5 +14,7 @@ if (file_exists($maintenance = __DIR__.'/../storage/framework/maintenance.php'))
 require __DIR__.'/../vendor/autoload.php';
 
 // Bootstrap Laravel and handle the request...
-(require_once __DIR__.'/../bootstrap/app.php')
-    ->handleRequest(Request::capture());
+/** @var Application $app */
+$app = require_once __DIR__.'/../bootstrap/app.php';
+
+$app->handleRequest(Request::capture());