Phase 16: Add optional remote-server mode for Raspberry Pi and home servers

[ashishsinghbora]

Goal

Allow the headless core to run on a remote machine while a browser or desktop UI controls it.

Scope

• Make bind address configurable but keep loopback as the default.
• Add explicit remote-mode configuration.
• Require authentication and secure transport guidance for non-loopback exposure.
• Add CORS/origin configuration with a deny-by-default policy.
• Document reverse-proxy deployment.
• Add health endpoint and graceful shutdown.
• Ensure remote clients cannot bypass the same authorization and filesystem restrictions as local clients.

Acceptance criteria

• Remote mode is opt-in.
• Documentation clearly warns against exposing the daemon directly to the public internet.
• Integration tests cover authenticated remote API access and rejected unauthenticated requests.