perf(seo): image sizes, semantic HTML, X-Robots-Tag headers

- Add `sizes` prop to 8 <Image> components across news, heritage, and
  application pages — tells the browser which srcset variant to download,
  improving LCP and reducing bandwidth
- Replace date <span> with <time dateTime={ISO}> on news pages —
  Google uses datetime for article freshness signals
- Wrap news cards and article content in <article> tags — semantic
  boundary for crawlers
- Add X-Robots-Tag: noindex, nofollow header to all /hq-command
  responses in proxy.ts — defense-in-depth alongside meta robots

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

src/proxy.ts

@@ -37,7 +37,9 @@ export async function proxy(request: NextRequest) {
         if (isPublicHQRoute) {
           return NextResponse.redirect(new URL('/hq-command/dashboard', request.url));
         }
-        return NextResponse.next(); // Pasa al CMS tranquilamente
+        const authedRes = NextResponse.next();
+        authedRes.headers.set('X-Robots-Tag', 'noindex, nofollow');
+        return authedRes;
       } catch (error) {
         // Pase falso o expirado
         if (!isPublicHQRoute) {
@@ -45,7 +47,9 @@ export async function proxy(request: NextRequest) {
         }
       }
     }
-    return NextResponse.next(); // Pasa a login/setup si no hay cookie
+    const hqRes = NextResponse.next();
+    hqRes.headers.set('X-Robots-Tag', 'noindex, nofollow');
+    return hqRes;
   }
 
   // --------------------------------------------------------