P0-2 + Phase A: drop Adsanity iframes, fix SEO baseline, noindex while staging

P0-2 (Adsanity iframe path removed):
- AdImage.tsx: deleted the iframe branch and the ADSANITY_CAMPAIGN_MAP
  fallback. AdImage now renders local images only; banners without a
  src render nothing.
- ads.ts: removed Ad.adsanity_id from the interface. Pruned AJA, Zixi,
  Lectrosonics, Opengear, Studio Hero, Magewell 300x250 and Blackmagic
  300x600 — they relied on ads.broadcastbeat.com which does not resolve.
  Surviving live banners: LiveU 728x90, LiveU PAYG 300x250, Telycam 300x250.
- SidebarAdStack: key no longer references the removed field.
- No banner_analytics rows reference ads.broadcastbeat.com.

Phase A (SEO baseline):
- robots.ts: fallback base URL now broadcastbeat.com (was rocket staging URL).
- sitemap.ts: fallback base URL now broadcastbeat.com (was bb-staging).
- news/[slug]/page.tsx and articles/[slug]/page.tsx: same fallback fix.
  JSON-LD now uses ISO 8601 for datePublished, absolute image URL via
  SITE_URL prefix, and publisher.logo points at /assets/images/logo.png
  instead of the 404-ing /legacy/site/broadcastbeat-logo.png.
- layout.tsx: removed the /en /es /pt /fr /de /zh /ja /ar /hi hreflang
  alternates - those routes 404 today; Phase D will reinstate. Replaced
  rocket.new Organization schema URL with broadcastbeat.com. Set
  robots index/follow=false until Phase B-D land and Rich Results passes.

Featured-image fallback hardening:
- legacy-source: rowToArticle now treats BB_Gray, no_image and placeholder
  URLs as null and falls back to the new placeholder so dead images do not
  leak through to the page.
- public/assets/images/article-placeholder.svg: new clean dark gradient
  with BroadcastBeat wordmark, NOT no_image.png style.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/articles/legacy-source.ts

@@ -28,7 +28,7 @@ interface ImportedPostRow {
   wp_published_at: string | null;
 }
 
-const FALLBACK_IMAGE = "/legacy/site/no_image.png";
+const FALLBACK_IMAGE = "/assets/images/article-placeholder.svg";
 
 // Tag → section mapping. Source: tag distribution observed in
 // bb.wp_imported_posts. Matches against any overlap (lowercased).
@@ -80,9 +80,16 @@ function readTime(content: string | null): string {
   return `${minutes} min read`;
 }
 
+// Featured-image URLs that we treat as "no image" — historical placeholders
+// that should resolve to the clean dark placeholder instead of the grey box.
+const BROKEN_IMAGE_PATTERNS = /no_image|BB_Gray|placeholder/i;
+
 function rowToArticle(row: ImportedPostRow, section: Section = "news"): Article {
-  const image = row.featured_image
-    ? rewriteLegacyImageUrl(row.featured_image)
+  const rawImage = row.featured_image && !BROKEN_IMAGE_PATTERNS.test(row.featured_image)
+    ? row.featured_image
+    : null;
+  const image = rawImage
+    ? rewriteLegacyImageUrl(rawImage)
     : FALLBACK_IMAGE;
   const content = rewriteLegacyImageUrlsInHtml(row.content || "");
   const author = row.author_name || "Staff Reporter";