feat(demo): funnel server-less users to the OpenCode Connect waitlist (#127)

The demo's only exit CTA was 'Connect your own server' — useless for the
majority of installers who have no server (the exact churn/retention segment).
Adds a secondary CTA pointing them to the OpenCode Connect (hosted, no-setup)
waitlist, which is the monetization funnel per the founder strategy. Additive,
reuses the existing waitlist on /connection/add and the demo's exit-tracking;
i18n en+zh in parity.


Claude-Session: https://claude.ai/code/session_01T12AhSnQVrSxNnvwfCx2z6

Co-authored-by: engineer <engineer@macbookpro.lan>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

src/lib/i18n/en.json

@@ -432,6 +432,7 @@
     "ctaTitle": "Like what you see?",
     "ctaSubtitle": "This was a scripted demo. Connect your own opencode server to do this for real.",
     "connectButton": "Connect your own server",
-    "setupGuideLink": "How to set up a server"
+    "setupGuideLink": "How to set up a server",
+    "hostedCtaLink": "No server? Join the OpenCode Connect waitlist — hosted, no setup"
   }
 }