fix: inline viewer bundle and add ES5 boot watchdog with retry

[kryptocodes]

Summary

Inline the noVNC bundle into liveview.html to remove the separate critical bundle.js request that caused stalls. Add a bounded boot watchdog with retry overlay, and relay boot diagnostics through embedding hosts.

Validation

• node --test images/minimal-vnc-desktop/kbd/test/host-embed-layout.test.mjs — 19 passed
• git diff --check — passed

Risk and Rollback

The viewer HTML is larger and no longer benefits from the immutable bundle cache. A failed boot may reload up to two times before showing an error. This retains the existing modern-browser requirement for the noVNC module.

Rollback by reverting the Dockerfile, liveview.html, viewer.js, proxy, and host bridge changes together.

Checklist

• I kept the change focused.
• I updated tests or documentation when needed.
• I did not include secrets, credentials, private infrastructure details, or production configuration.
• I noted any license, security, or privacy considerations.