Init multiplayer

server/README.md

@@ -0,0 +1,33 @@
+# Realtime Sessions
+
+This app now supports shared sessions by `gameId` using a lightweight WebSocket server.
+
+## Run
+
+```bash
+npm run realtime:server
+```
+
+Default port: `8787`  
+Override: `REALTIME_PORT=9000 npm run realtime:server`
+
+## Nginx Proxy
+
+Proxy `/realtime/*` from your public domain to the realtime server:
+
+```nginx
+location /realtime/ {
+    proxy_pass http://127.0.0.1:8787/;
+    proxy_http_version 1.1;
+    proxy_set_header Upgrade $http_upgrade;
+    proxy_set_header Connection "upgrade";
+    proxy_set_header Host $host;
+    proxy_set_header X-Real-IP $remote_addr;
+    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+    proxy_set_header X-Forwarded-Proto $scheme;
+}
+```
+
+Notes:
+- `proxy_pass` with trailing `/` is important, because frontend calls `/realtime/sessions` and `/realtime/ws`.
+- Sessions are kept in memory; restarting the realtime server resets all active game sessions.