Show the password generator in the website's screenshots

The desktop upload shot fills the password with Generate, and the share
created shot now comes from creating that share, so the password is
offered beside the link. The created share takes a fixed token, so its
link and QR code read the same on every run, and is deleted before the
dashboard shot, which no longer counts the unfinished upload in its disk
usage.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/Screenshots/DemoData.php

@@ -24,6 +24,9 @@ final class DemoData
 
     public const PROTECTED_PASSWORD = 'autumn-harbour-42';
 
+    /** The share the desktop upload creates, so its link and QR code read the same on every run. */
+    public const CREATED_TOKEN = 'Tf8gH2jK4mN6pQ3r';
+
     public static function admin(): User
     {
         return User::factory()->admin()->create([