feat: add CAMOFOX_NET_INTERFACE to bind server to specific network interface

[aadamowski]

This adds a new environment variable CAMOFOX_NET_INTERFACE that allows configuring which network interface the server should listen on.

By default, it listens on all interfaces (empty string), but can be configured to listen only on loopback (127.0.0.1) for improved security.

Fixes security issue where server was always listening on all network interfaces, which could expose the service to unauthorized access from other machines on the same network.

Usage:

  CAMOFOX_NET_INTERFACE=127.0.0.1 npm start  # Loopback only (secure)

  CAMOFOX_NET_INTERFACE=0.0.0.0 npm start    # All interfaces (explicit)

  npm start                                  # All interfaces (default)

Testing:

• Unit tests: npm test -- tests/unit/config.test.js tests/unit/serverBinding.test.js
• Added 6 new tests covering configuration parsing and server binding behavior
• Integration tests verify actual Express server binds to correct interfaces
• Functional testing performed with these exact commands:
  • Launch loopback: CAMOFOX_PORT=9380 CAMOFOX_NET_INTERFACE=127.0.0.1 npm start
  • Verify binding: ss -tlpn 'sport = 9380' # Shows 127.0.0.1:9380
  • Test access: curl -s http://127.0.0.1:9380/health
  • Launch default: CAMOFOX_PORT=9381 npm start
  • Verify binding: ss -tlpn 'sport = 9381' # Shows *:9381
  • Test access: curl -s http://127.0.0.1:9381/health

All tests pass, backward compatibility preserved.

[skyfallsin]

Thank you — this is now superseded by merged #8096. Current master supports configurable binding via CAMOFOX_BIND_HOST, forwards it through launched server subprocesses, documents the setting, and includes the effective listener address in startup logs and the server:started event. We kept the existing all-interface default for container compatibility.