Add Vercel launch path for Phu AI Core static app

[Copilot]

This updates the Fastcash / Phu AI Core static app so it can be launched directly on Vercel and avoids breaking page startup in static-hosted environments. It also makes the deployment path discoverable in both the UI and docs.

• Vercel launch entry point

  • Adds a header CTA in index.html that opens a prefilled Vercel clone/deploy flow for phuquoc81/Fastcash.
  • Adds a minimal vercel.json to keep the static deployment behavior explicit.

• Static-host-safe telemetry bootstrap

  • Stops unconditional telemetry startup on page load for static deployments.
  • Makes telemetry opt-in via query param or persisted preference.
  • Guards browser-only storage access so restricted contexts do not throw during startup.
  • Removes direct reliance on runtime process.env assumptions in browser code.

• Documentation

  • Adds a Vercel deploy button and a short “Launching Phu AI Core on Vercel” section to README-WEBAPP.md.
  • Updates TELEMETRY_SETUP.md to describe the new opt-in telemetry behavior for static/Vercel launches.

<a
  href="https://vercel.com/new/clone?repository-url=https://github.com/phuquoc81/Fastcash&project-name=phu-ai-core&repository-name=Fastcash"
  target="_blank"
  rel="noopener noreferrer"
  class="fc-btn fc-btn-secondary fc-header-cta"
>
  ▲ Launch Phu AI Core on Vercel
</a>

• Files touched
  • index.html
  • otel-init.js
  • README-WEBAPP.md
  • TELEMETRY_SETUP.md
  • styles.css
  • vercel.json

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