Add browser tests for the Material interface

Upload drop zone, copying a share link, unlocking a download on a phone,
sorting and deleting on the admin dashboard, and the system theme with
the Appearance picker.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01V9NnLxnPp8vaaurb3Z1MFy

tests/Pest.php

@@ -21,7 +21,7 @@ pest()->extend(TestCase::class)
         // EnsureSetupComplete middleware redirects to /setup unless an admin exists.
         User::factory()->admin()->create(['email' => 'admin-setup@test.com']);
     })
-    ->in('Feature');
+    ->in('Feature', 'Browser');
 
 /*
 |--------------------------------------------------------------------------