Add remote MQTT control gateway and standalone UI

[arvindh123]

Summary

Adds remote control of the agent over MQTT together with an HTTP/WebSocket gateway and standalone web UI.

What changed

• Added the remote-control protocol, JSON-RPC operations, MQTT transport, job lifecycle, state/event persistence, command execution, terminal streaming, OTA handling, and related tests.
• Added the gateway service that bridges authenticated browser HTTP/WebSocket requests to MQTT.
• Added standalone UI and container images/configuration for the UI and gateway.
• Added AsyncAPI/OpenRPC definitions and JSON schemas for remote protocol messages.
• Updated agent configuration, Docker Compose deployment, bootstrap/Atom integration, device/service APIs, and operational documentation.
• Added MQTT ACL, remote protocol, standalone UI, and quick-start documentation.

Why

Provides a deployable browser-to-agent control path for remote state, jobs, terminal access, logs, OTA, and configuration while keeping the agent-facing transport MQTT-based.

Validation

• npm run typecheck: passed
• Docker Compose configuration validation: passed
• Go tests: gateway and remote packages passed; tests requiring local HTTP/UDP sockets were blocked by the execution sandbox
• npm run lint: reports formatting-only violations in:
  • ui/src/lib/transport.ts
  • ui/src/pages/ota.tsx