refactor(frontend): migrate from Vite to Nuxt SPA

Replace Vite and Vue Router with Nuxt framework
Update Docker, build scripts, and env vars for Nuxt generate

frontend/server/routes/robots.txt.ts

@@ -0,0 +1,7 @@
+import { normalizeSiteUrl, robotsTxt } from '../utils/seo-files';
+
+export default defineEventHandler((event) => {
+  const config = useRuntimeConfig(event);
+  setHeader(event, 'Content-Type', 'text/plain; charset=utf-8');
+  return robotsTxt(normalizeSiteUrl(config.public.siteUrl));
+});