feat(panel): serve authenticated app on dedicated panel subdomain

Separate the marketing landing site from the authenticated app by host.
Next.js middleware reads PANEL_HOST/LANDING_HOST at runtime and redirects
authenticated routes (/dashboard, /login, /register) from the landing host
to the panel host, and the landing root on the panel host to /dashboard.
Disabled (single-origin) when PANEL_HOST is unset, so local dev is unchanged.

Helm: add ingress.panel.host with a third ingress rule + TLS host routing to
the frontend service, pass LANDING_HOST/PANEL_HOST to the frontend, and append
the panel origin to the backend CORS list (frontend URL stays first so
PLATFORM_DOMAIN resolution is unaffected).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/middleware.ts

@@ -14,6 +14,33 @@ function parseAcceptLanguage(header: string | null): string[] {
     .map((x) => x.tag);
 }
 
+// Host-based separation between the marketing landing site and the
+// authenticated panel. Configured at runtime (server-side) so the same
+// frontend image can serve both hosts. When PANEL_HOST is unset (local dev),
+// host routing is disabled and everything is served from a single origin.
+const PANEL_HOST = process.env.PANEL_HOST?.trim().toLowerCase();
+const LANDING_HOST = process.env.LANDING_HOST?.trim().toLowerCase();
+
+// Locale-stripped path prefixes that belong to the authenticated panel.
+const PANEL_PATH_PREFIXES = ['/dashboard', '/login', '/register'];
+
+function stripLocale(pathname: string): string {
+  for (const l of locales) {
+    if (pathname === `/${l}`) return '/';
+    if (pathname.startsWith(`/${l}/`)) return pathname.slice(l.length + 1);
+  }
+  return pathname;
+}
+
+function isPanelPath(pathname: string): boolean {
+  const p = stripLocale(pathname);
+  return PANEL_PATH_PREFIXES.some((pre) => p === pre || p.startsWith(`${pre}/`));
+}
+
+function hostOf(request: NextRequest): string {
+  return (request.headers.get('host') || '').split(':')[0].toLowerCase();
+}
+
 function detectLocale(request: NextRequest): Locale {
   // 1. Explicit choice via cookie
   const cookieLocale = request.cookies.get(LOCALE_COOKIE)?.value;
@@ -33,18 +60,42 @@ function detectLocale(request: NextRequest): Locale {
 }
 
 export function middleware(request: NextRequest) {
-  const { pathname } = request.nextUrl;
+  const { pathname, search } = request.nextUrl;
 
+  // 1. Ensure a locale prefix (e.g. /login -> /fa-IR/login). On the redirect
+  //    the host is preserved, so host routing (below) runs on the next request.
   const pathnameHasLocale = locales.some(
     (locale) => pathname === `/${locale}` || pathname.startsWith(`/${locale}/`),
   );
-  if (pathnameHasLocale) return;
+  if (!pathnameHasLocale) {
+    const locale = detectLocale(request);
+    request.nextUrl.pathname = `/${locale}${pathname === '/' ? '' : pathname}`;
+    const response = NextResponse.redirect(request.nextUrl);
+    response.cookies.set(LOCALE_COOKIE, locale, { path: '/', maxAge: 60 * 60 * 24 * 365 });
+    return response;
+  }
 
-  const locale = detectLocale(request);
-  request.nextUrl.pathname = `/${locale}${pathname === '/' ? '' : pathname}`;
-  const response = NextResponse.redirect(request.nextUrl);
-  response.cookies.set(LOCALE_COOKIE, locale, { path: '/', maxAge: 60 * 60 * 24 * 365 });
-  return response;
+  // 2. Host-based separation between the landing site and the panel.
+  //    Disabled entirely unless PANEL_HOST is configured (local dev).
+  if (PANEL_HOST) {
+    const host = hostOf(request);
+    const panelPath = isPanelPath(pathname);
+
+    // Authenticated routes requested on the landing host -> move to the panel.
+    if (LANDING_HOST && host === LANDING_HOST && panelPath) {
+      return NextResponse.redirect(`https://${PANEL_HOST}${pathname}${search}`, 308);
+    }
+
+    // Marketing pages requested on the panel host -> send to the dashboard.
+    if (host === PANEL_HOST && !panelPath) {
+      const locale = pathname.split('/')[1]; // path is already locale-prefixed
+      const target = request.nextUrl.clone();
+      target.pathname = `/${locale}/dashboard`;
+      return NextResponse.redirect(target);
+    }
+  }
+
+  return;
 }
 
 export const config = {