fix: 7 bug fixes + port config with auto-restart

- HTTPException import added (was causing 500 on missing dashboard)
- game_manager.remove_plugin() restored (was AttributeError)
- api.js checks HTTP status codes, fails fast on errors
- sidebar game highlight only matches selected gameId
- scene resize handler uses stored canvas dims (was NaN)
- forwarder socket properly closed on listener stop
- telemetry port: use_unified_port toggle, off = per-game port, auto-restart on switch

templates/scene.html

@@ -124,8 +124,6 @@
             }
 
             window.addEventListener('resize', () => {
-                const cw = parseInt(sceneCanvas.style.width) / (parseInt(sceneCanvas.style.width) / 1920) || 1920;
-                const ch = parseInt(sceneCanvas.style.height) / (parseInt(sceneCanvas.style.height) / 1080) || 1080;
                 const vw = window.innerWidth;
                 const vh = window.innerHeight;
                 const scale = Math.min(vw / cw, vh / ch);