Increase file upload validation limits

- EntregaController: max:2048 -> max:20480 (2MB -> 20MB)
- UpdateUserProfileInformation: max:1024 -> max:5120 (1MB -> 5MB)

The server-level limits (nginx client_max_body_size and php.ini) were
already raised in the previous commit; these Laravel validation rules
were the remaining bottleneck blocking uploads over 2MB.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/Http/Controllers/EntregaController.php

@@ -71,7 +71,7 @@ class EntregaController extends Controller
     public function store(Request $request, Tarea $tarea)
     {
         $request->validate([
-            'archivo' => 'nullable|file|max:2048',
+            'archivo' => 'nullable|file|max:20480',
             'texto'   => 'nullable|string|max:5000',
         ]);