This PR adds Unix Domain Socket (UDS) listening and BaseUrl subpath support to v2rayA, primarily adapting for FnOS gateway and similar reverse-proxy environments.
Why this is needed:

• UDS Support: Avoids exposing TCP ports locally, allowing safer and more efficient Unix socket communication with local gateways.

• BaseUrl Support: Fixes 404 Not Found issues for web static assets (/static/*) and WebSockets (/api/message) when v2rayA is hosted under a reverse-proxy subpath (e.g. https://nas.local/v2raya-sub/).
  Key Changes:

• Go Backend:

  • Added V2RAYA_SOCKET/--socket and V2RAYA_BASEURL/--baseurl options.
  • Mounted routes (auth, noAuth, and ServeGUI) under the BaseUrl group.
  • Enabled net.Listen("unix", ...) and chmod 0777 on the socket file.
  • Adapted registerEmbeddedRoute to dynamically strip the BasePath prefix from static assets.

• Frontend GUI:

  • Adjusted connectWsMessage and backendPort.js to dynamically detect and use the subpath prefix for API & WS connections.
  • Relaxed the input verification pattern in server address settings to support relative path prefixes.
    Compatibility Guarantee & Test Proofs:

• Strict Backward Compatibility:
  We have conducted comprehensive regression testing on the default startup scenario. When running without the new UDS (--socket) or BaseUrl (--baseurl) options, v2rayA behaves 100% identically as before—strictly keeping TCP listening at 0.0.0.0:2017 and root routing at /. There is absolutely zero deviation in API endpoints or WebSocket handshakes under default configurations, guaranteeing a safe upgrade paths with no regressions.

• Test Screenshots:

  • Test 1: Default TCP Mode Verification (100% Normal)
    

  • Test 2: Unix Domain Socket + BaseUrl Subpath Mode Verification (100% Normal)