fix(ui): prefer Compose env values and polish error pages

When a managed variable shares a Compose-defined key, show the
hardcoded Compose value as read-only and exclude it from managed
rows. Render Contact support as a button, use the collapsible
component for 419 proxy help, and style its list/code markers.

tests/Feature/ErrorPagesRedesignTest.php

@@ -57,9 +57,22 @@ it('uses login as primary action on session expired page', function () {
         ->toContain('/login')
         ->toContain('Back to login')
         ->toContain('Using a reverse proxy or Cloudflare Tunnel?')
+        ->toContain('x-data="{ open: false }"')
+        ->toContain('x-on:click="open = !open"')
+        ->toContain('livewire.js')
         ->not->toContain('>Dashboard</');
 });
 
+it('renders contact support as a button', function () {
+    $exception = new HttpException(404, 'Not found');
+
+    $html = view('errors.404', ['exception' => $exception])->render();
+
+    expect($html)
+        ->toContain('href="'.config('constants.urls.contact').'"')
+        ->toMatch('/<button[^>]*>\s*Contact support/s');
+});
+
 it('shows purified exception message on 500 page', function () {
     $exception = new RuntimeException('Database connection failed');