fix: UI auto-detects server port from page origin (#55)

The UI had hardcoded localhost:8080 for HTTP and localhost:8765 for
WebSocket, causing "Backend unavailable" when served from Docker
(port 3000) or any non-default port.

Changes:
- api.config.js: BASE_URL now uses window.location.origin instead
  of hardcoded localhost:8080
- api.config.js: buildWsUrl() uses window.location.host instead of
  hardcoded localhost:8080
- sensing.service.js: WebSocket URL derived from page origin instead
  of hardcoded localhost:8765
- main.rs: Added /ws/sensing route to the HTTP server so WebSocket
  and REST are reachable on a single port

Fixes #55

Co-Authored-By: claude-flow <ruv@ruv.net>

rust-port/wifi-densepose-rs/crates/wifi-densepose-sensing-server/src/main.rs

@@ -2091,6 +2091,8 @@ async fn main() {
         // Stream endpoints
         .route("/api/v1/stream/status", get(stream_status))
         .route("/api/v1/stream/pose", get(ws_pose_handler))
+        // Sensing WebSocket on the HTTP port so the UI can reach it without a second port
+        .route("/ws/sensing", get(ws_sensing_handler))
         // Static UI files
         .nest_service("/ui", ServeDir::new(&ui_path))
         .layer(SetResponseHeaderLayer::overriding(