fix(ui): revert vite base /app/ — broke CSS/JS asset loading

Keep nginx /app/ alias for favicon resolution only.
CSS/JS stay at root-relative paths via location /.

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

index.html

@@ -9,8 +9,8 @@
 <meta name="apple-mobile-web-app-status-bar-style" content="black-translucent">
 <meta name="apple-mobile-web-app-title" content="NovaSonic">
 <link rel="manifest" href="manifest.json">
-<link rel="icon" href="%BASE_URL%icon.svg" type="image/svg+xml">
-<link rel="icon" href="%BASE_URL%icon-192.png" type="image/png" sizes="192x192">
+<link rel="icon" href="icon.svg" type="image/svg+xml">
+<link rel="icon" href="icon-192.png" type="image/png" sizes="192x192">
 <link rel="apple-touch-icon" href="icon.svg">
 <title>NovaSonic</title>
 <link rel="preconnect" href="https://fonts.googleapis.com">