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

app.py

@@ -5,7 +5,7 @@ import os
 from contextlib import asynccontextmanager
 from pathlib import Path
 
-from fastapi import FastAPI, WebSocket, WebSocketDisconnect, Request
+from fastapi import FastAPI, HTTPException, WebSocket, WebSocketDisconnect, Request
 from fastapi.staticfiles import StaticFiles
 from fastapi.templating import Jinja2Templates
 from fastapi.responses import HTMLResponse, FileResponse