feat(seo/geo): Dataset + Article + BreadcrumbList structured data, noindex archive

GEO (AI answer engines) — make the signal feeds and case studies machine-citeable:
- Dataset JSON-LD on /trump, /kol, /trades (creator=Endorphin, publisher→#org,
  isAccessibleForFree, temporalCoverage). These are the "data/history/track
  record" entities Perplexity/Gemini/ChatGPT cite.
- case-studies: ItemList of 5 Article nodes, each with headline/description/
  articleBody/about + citation→evidence URL + author=Endorphin. ISO dates
  derived where parseable, omitted for vague labels.
- public/llms-full.txt: single-doc full reference (methodology + glossary +
  case studies w/ sources inlined) for one-fetch AI ingestion; linked from llms.txt.

SEO:
- Breadcrumbs component (components/seo/Breadcrumbs.tsx) → BreadcrumbList JSON-LD
  on the 8 indexable content pages (trump/kol/macro/trades/analytics/
  methodology/glossary/case-studies).
- /archive split into server page + ArchivePageClient; server page sets
  robots noindex (legacy/test data — thin-content risk).
- openGraph added to /trades and /analytics (previously meta+canonical only).

Verified: tsc 0 errors, next build passes, runtime curl confirms all JSON-LD
types render and llms-full.txt serves 200. No trading/API/component-logic changes.

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

app/[locale]/case-studies/page.tsx

@@ -1,5 +1,6 @@
 import type { Metadata } from 'next'
 import Link from 'next/link'
+import Breadcrumbs from '@/components/seo/Breadcrumbs'
 
 const siteUrl = process.env.NEXT_PUBLIC_SITE_URL || 'https://trumpsignal.com'
 
@@ -303,13 +304,60 @@ const SIGNAL_COLOR: Record<string, string> = {
   DIVERGENCE: '#f5a524',
 }
 
+// Map a free-text case date ("March 2, 2025", "April 2025", "Illustrative
+// composite") to an ISO date where possible. Returns undefined for vague /
+// non-date labels so we omit datePublished rather than emit garbage.
+function caseIsoDate(raw: string): string | undefined {
+  const d = new Date(raw)
+  return isNaN(d.getTime()) ? undefined : d.toISOString().slice(0, 10)
+}
+
 export default async function CaseStudiesPage({ params }: { params: Promise<{ locale: string }> }) {
   const { locale } = await params
   const copy = getCopy(locale)
   const isZh = false  // i18n shelved — Chinese branches kept as dead code for future revival; see messages/zh.json
 
+  // ── GEO: each case as a schema.org/Article in an ItemList ─────────────────
+  // These documented event walkthroughs are exactly what AI answer engines
+  // (Perplexity, Gemini, ChatGPT) cite for "did Trump posts move crypto"
+  // queries. Structured data makes them machine-citeable. Evidence URLs become
+  // citation links; Endorphin is the author/publisher.
+  const pageUrl = `${siteUrl}/${locale}/case-studies`
+  const caseJsonLd = {
+    '@context': 'https://schema.org',
+    '@type': 'ItemList',
+    '@id': `${pageUrl}#cases`,
+    name: copy.title,
+    description: copy.description,
+    itemListElement: copy.cases.map((c, i) => {
+      const iso = caseIsoDate(c.date)
+      const article: Record<string, unknown> = {
+        '@type': 'Article',
+        '@id': `${pageUrl}#${c.id}`,
+        headline: c.title,
+        description: c.summary,
+        articleBody: c.detail,
+        about: c.asset,
+        author: { '@type': 'Organization', name: 'Endorphin', url: siteUrl },
+        publisher: { '@id': `${siteUrl}/#org` },
+        isPartOf: { '@id': `${siteUrl}/#website` },
+      }
+      if (iso) article.datePublished = iso
+      if (c.externalUrl) {
+        article.citation = c.externalUrl
+        article.isBasedOn = c.externalUrl
+      }
+      return { '@type': 'ListItem', position: i + 1, item: article }
+    }),
+  }
+
   return (
     <div className="page" style={{ maxWidth: 780 }}>
+      <script
+        type="application/ld+json"
+        dangerouslySetInnerHTML={{ __html: JSON.stringify(caseJsonLd) }}
+      />
+      <Breadcrumbs items={[{ name: copy.heroTitle, path: `/${locale}/case-studies` }]} />
       <div className="page-head">
         <div>
           <h1 className="page-title">{copy.heroTitle}</h1>