feat(i18n): nl at root URLs + keep devtools in the docker demo

Serve the source locale (nl) at / instead of /nl/: angular.json sourceLocale is now
{ code: 'nl', subPath: '' } → nl output at browser/ root (base href /), en stays /en/.
Rework localeLinks (nl → bare path, en → /en/…) + spec, and serve-i18n.mjs (nl assets at
root, en under /en/, / serves the nl index). And build the docker demo (+ serve:i18n) with
`--configuration development --localize` so isDevMode() stays true and the dev `⚙ state`
panel + role/scenario switchers render in the localized compose demo (they were correctly
gated off in the previous production build). Verified: nl base href /, en /en/, ngDevMode present.

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

scripts/serve-i18n.mjs

@@ -52,25 +52,23 @@ createServer(async (req, res) => {
     return;
   }
   const url = decodeURIComponent(rawUrl.split('?')[0]);
-  // Landing at / has no locale bundle — redirect to Dutch.
-  if (url === '/') {
-    res.writeHead(302, { location: '/nl/' });
-    return res.end();
-  }
   const rel = normalize(url).replace(/^(\.\.[/\\])+/, ''); // no path traversal
-  const locale = url.startsWith('/en/') ? 'en' : 'nl';
+  // nl (source) is served at the ROOT (subPath ''); en lives under /en/.
+  const isEn = url === '/en' || url.startsWith('/en/');
+  const indexPath = isEn ? join(ROOT, 'en', 'index.html') : join(ROOT, 'index.html');
   try {
+    // A real asset (nl at root, en under /en/) — otherwise fall through to the SPA index.
+    if (url === '/' || url === '/en' || url === '/en/') throw new Error('serve index');
     const file = await readFile(join(ROOT, rel));
     send(res, 200, file, MIME[extname(rel)] ?? 'application/octet-stream');
   } catch {
     // SPA fallback to the requested locale's index.html.
     try {
-      const index = await readFile(join(ROOT, locale, 'index.html'));
-      send(res, 200, index, 'text/html');
+      send(res, 200, await readFile(indexPath), 'text/html');
     } catch {
       send(res, 404, 'Not found', 'text/plain');
     }
   }
 }).listen(PORT, () => {
-  console.log(`Serving ${ROOT} at http://localhost:${PORT}/  (→ /nl/, /en/)`);
+  console.log(`Serving ${ROOT} at http://localhost:${PORT}/  (nl at /, en at /en/)`);
 });