delete sampleArticles seed; serve all sections from bb.wp_imported_posts (DB)

Eliminates 72 hardcoded rocket.new image refs in one shot. Section pages
(/gear, /technology, /show-coverage, /news) now render from
bb.wp_imported_posts via getLegacyArticlesBySection(section), which maps
each non-news section to a curated tag set (e.g. gear -> Audio, Cameras,
lighting, Blackmagic Design, monitoring; technology -> AI, Streaming,
OTT, IP, Cloud, AV; show-coverage -> NAB, IBC, BroadcastAsia).

Also:
- src/lib/articles/types.ts: Article interface lifted out of the deleted
  seed file. Type-only consumers (NewsArticleDetailClient,
  ArticleDetailClient, legacy-source) re-imported from here.
- /news (client component) now wrapped: server fetches articles from DB
  and passes to NewsPageClient. Filter UI unchanged.
- generateStaticParams on /news/[slug] and /articles/[slug] no longer
  references seed slugs; pre-renders 50 most-recent imported slugs and
  relies on dynamicParams + revalidate=3600 for the rest.
- sitemap.ts now sources article URLs from
  getLegacyRecentSitemapEntries() (up to 5000 most-recent imported posts).
  Default BASE_URL fallback updated from the rocket.new placeholder to
  bb-staging.onsethost.com.
- src/app/api/ai/article-suggestions/route.ts now pulls candidates from
  the DB (top 100 recent news) and resolves AI-returned slugs via DB
  lookup if not in the candidate window.

Inline rocket.new image refs in homepage components (ArticleFeed,
FeaturedBento) are unchanged in this commit; those are inline seed
arrays in the components, not imports of sampleArticles.

src/app/sitemap.ts

@@ -1,7 +1,7 @@
 import { MetadataRoute } from 'next';
-import { sampleArticles } from '@/lib/articles/sampleArticles';
+import { getLegacyRecentSitemapEntries } from '@/lib/articles/legacy-source';
 
-const BASE_URL = process.env.NEXT_PUBLIC_SITE_URL || 'https://broadcastb5322.builtwithrocket.new';
+const BASE_URL = process.env.NEXT_PUBLIC_SITE_URL || 'https://bb-staging.onsethost.com';
 
 export default async function sitemap(): Promise<MetadataRoute.Sitemap> {
   // Static pages
@@ -23,13 +23,26 @@ export default async function sitemap(): Promise<MetadataRoute.Sitemap> {
     { url: `${BASE_URL}/terms`, lastModified: new Date(), changeFrequency: 'yearly', priority: 0.3 },
   ];
 
-  // Dynamic article pages — all published articles
-  const articlePages: MetadataRoute.Sitemap = sampleArticles.map((article) => ({
-    url: `${BASE_URL}/articles/${article.slug}`,
-    lastModified: new Date(article.date) || new Date(),
-    changeFrequency: 'monthly' as const,
-    priority: 0.7,
-  }));
+  // Dynamic article pages — sourced from bb.wp_imported_posts (DB).
+  const articleEntries = await getLegacyRecentSitemapEntries(5000);
+  const articlePages: MetadataRoute.Sitemap = articleEntries.flatMap(({ slug, date }) => {
+    const lastModified = new Date(date);
+    const safe = isNaN(lastModified.getTime()) ? new Date() : lastModified;
+    return [
+      {
+        url: `${BASE_URL}/news/${slug}`,
+        lastModified: safe,
+        changeFrequency: 'monthly' as const,
+        priority: 0.7,
+      },
+      {
+        url: `${BASE_URL}/articles/${slug}`,
+        lastModified: safe,
+        changeFrequency: 'monthly' as const,
+        priority: 0.6,
+      },
+    ];
+  });
 
   // Attempt to ping Google Search Console (fire-and-forget, non-blocking)
   const sitemapUrl = encodeURIComponent(`${BASE_URL}/sitemap.xml`);