Fix drag-to-move and WS keepalive

drag-to-move: use window-level mousemove/mouseup listeners for reliable
drag detection — React synthetic events on container were unreliable

WS keepalive: server sends ping JSON every 25s so nginx proxy_read_timeout
never fires; client ignores pings (not broadcast to peers anymore)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/routes/ws.ts

@@ -6,6 +6,8 @@ import type { RawData } from 'ws'
 // hotel slug → set of connected streams
 const hotelRooms = new Map<string, Set<SocketStream>>()
 
+const PING_INTERVAL_MS = 25_000 // ping every 25s — keeps nginx proxy_read_timeout alive
+
 const ws: FastifyPluginAsync = async (fastify) => {
   await fastify.register(fastifyWebsocket)
 
@@ -19,8 +21,21 @@ const ws: FastifyPluginAsync = async (fastify) => {
       if (!hotelRooms.has(hotel)) hotelRooms.set(hotel, new Set())
       hotelRooms.get(hotel)!.add(connection)
 
+      // Send periodic ping so nginx proxy_read_timeout never fires
+      const pingTimer = setInterval(() => {
+        if (connection.socket.readyState === 1) {
+          connection.socket.send(JSON.stringify({ type: 'ping' }))
+        }
+      }, PING_INTERVAL_MS)
+
       connection.socket.on('message', (raw: RawData) => {
         const data = raw.toString()
+        // Ignore client pings — no need to broadcast them
+        try {
+          const msg = JSON.parse(data) as { type?: string }
+          if (msg.type === 'ping') return
+        } catch { /* not JSON, fall through */ }
+
         const peers = hotelRooms.get(hotel)
         if (!peers) return
         peers.forEach(peer => {
@@ -31,6 +46,7 @@ const ws: FastifyPluginAsync = async (fastify) => {
       })
 
       connection.socket.on('close', () => {
+        clearInterval(pingTimer)
         hotelRooms.get(hotel)?.delete(connection)
         if (hotelRooms.get(hotel)?.size === 0) hotelRooms.delete(hotel)
       })