Add server control (start/stop/restart, live logs, broadcast, kick) to webadmin

Docker SDK drives login/char/worldserver containers via docker.sock (mounted
read-only into webadmin); live logs stream over SSE with nginx buffering
disabled so lines arrive in real time. Broadcast/kick go through a new
admin_queue DB table that the world server polls every ~2s in its existing
WorldProcess tick loop, avoiding a second IPC channel to the game server.

webadmin/Dockerfile

@@ -9,4 +9,4 @@ COPY app.py ./
 COPY templates ./templates
 
 EXPOSE 8080
-CMD ["gunicorn", "--bind", "0.0.0.0:8080", "--workers", "2", "app:app"]
+CMD ["gunicorn", "--bind", "0.0.0.0:8080", "--workers", "2", "--worker-class", "gthread", "--threads", "8", "app:app"]