feat: Wire up brand kit — favicon, logos, and hero mark across all layouts

Copies brand assets to frontend/public (favicon.png, logo.png, logo-hero.png).
Updates index.html, LoginView, RegisterView, DashboardLayout sidebar, and
PublicLayout footer with proper branding.

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

frontend/src/views/auth/LoginView.vue

@@ -44,8 +44,7 @@ async function handleLogin() {
       <div class="bg-neutral-900 border border-neutral-800 rounded-lg p-8">
         <!-- Branding -->
         <div class="text-center mb-8">
-          <h1 class="text-3xl font-bold tracking-widest text-red-500">CORROSION</h1>
-          <p class="text-sm text-neutral-500 mt-2">Server Management Panel</p>
+          <img src="/logo-hero.png" alt="Corrosion Management" class="h-32 mx-auto mb-2" />
         </div>
 
         <!-- Error message -->