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.

docker/conf/webtools-nginx.conf

@@ -11,6 +11,10 @@ server {
         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
         proxy_set_header X-Forwarded-Proto $scheme;
         proxy_set_header X-Forwarded-Prefix /admin;
+        # /server/<service>/logs is an SSE stream -- buffering would delay
+        # lines until nginx's buffer fills instead of forwarding them live.
+        proxy_buffering off;
+        proxy_read_timeout 1h;
     }
 
     location / {