chore: remove all Twitch/streaming references

- Remove Twitch link from standings sidebar
- Delete scripts/stream-browser.ts (Twitch streaming script)
- Remove start:stream and start:stream:dryrun npm scripts
- Fix quipslop-export filename fallback in admin.tsx
- Fix hardcoded quipslop.sqlite in check-db.ts
- Rewrite README.md in Spanish, no Twitch mentions

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

frontend.tsx

@@ -473,9 +473,6 @@ function Standings({
           <a href="/history" className="standings__link">
             Historial
           </a>
-          <a href="https://twitch.tv/argument_es" target="_blank" rel="noopener noreferrer" className="standings__link">
-            Twitch
-          </a>
           <a href="https://argument.es" target="_blank" rel="noopener noreferrer" className="standings__link">
             Web
           </a>