fix(seo/geo): canonical URLs, OG KOL count, FAQ key-storage copy, expand llms.txt

SEO fixes:
- canonical on trump/macro/kol pages now hardcodes /en/ instead of
  /${locale}/ — prevents /zh/* routes (i18n shelved, routes still resolve)
  from generating duplicate-content signals pointing to /zh/ canonicals
- OG image: "15 KOL feeds" → "19" (matches kol_substack.py KOL_FEEDS count)
- FAQ JSON-LD: corrected API key storage description ("stored encrypted in
  your browser's local settings" was wrong — key is server-side encrypted,
  not stored in the browser)

GEO (Generative Engine Optimization):
- llms.txt fully rewritten: +full KOL list (all 19 named), +explicit
  differentiation section, +who-this-is-for, +technology stack detail
  (model names, price sources, DB), +Hyperliquid and isolated-margin
  definitions. AI crawlers (Perplexity, ChatGPT, Claude) use this file
  directly when answering questions about the product.

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

app/opengraph-image.tsx

@@ -153,7 +153,7 @@ export default function OGImage() {
         >
           {[
             { v: '<3s', l: 'post → position' },
-            { v: '15', l: 'KOL feeds' },
+            { v: '19', l: 'KOL feeds' },
             { v: '$0', l: 'platform fee' },
           ].map((s) => (
             <div key={s.l} style={{ display: 'flex', gap: 10, alignItems: 'baseline' }}>