feat: 실시간 대기 번호표 웹앱 초기 커밋

PIN 기반 세션으로 관리자·발급기·표시판 3개 역할을 하나의 앱에서 운영.
Socket.IO 실시간 동기화, Podman Quadlet(10.89.0.25) 배포 구성 포함.

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

server.js

@@ -0,0 +1,71 @@
+const express = require('express');
+const http = require('http');
+const { Server } = require('socket.io');
+const path = require('path');
+
+const app = express();
+const server = http.createServer(app);
+const io = new Server(server, {
+  pingTimeout: 60000,
+  pingInterval: 25000,
+});
+
+app.use(express.static(path.join(__dirname, 'public')));
+
+// pin -> { issuedCount, calledCount }
+const sessions = {};
+
+function sessionState(pin) {
+  const s = sessions[pin] || { issuedCount: 0, calledCount: 0 };
+  return {
+    issuedCount: s.issuedCount,
+    calledCount: s.calledCount,
+    waitingCount: s.issuedCount - s.calledCount,
+  };
+}
+
+io.on('connection', (socket) => {
+  let pin = null;
+
+  socket.on('join', ({ pin: p }) => {
+    if (!p || typeof p !== 'string' || p.length < 4) {
+      socket.emit('join_error', 'PIN은 최소 4자리 이상이어야 합니다.');
+      return;
+    }
+    pin = p.trim();
+    if (!sessions[pin]) {
+      sessions[pin] = { issuedCount: 0, calledCount: 0 };
+    }
+    socket.join(pin);
+    socket.emit('join_ok', sessionState(pin));
+  });
+
+  socket.on('issue_ticket', () => {
+    if (!pin || !sessions[pin]) return;
+    sessions[pin].issuedCount += 1;
+    const ticketNumber = sessions[pin].issuedCount;
+    const state = sessionState(pin);
+    socket.emit('ticket_issued', { ticketNumber, waitingCount: state.waitingCount });
+    io.to(pin).emit('state_update', state);
+  });
+
+  socket.on('call_next', () => {
+    if (!pin || !sessions[pin]) return;
+    const s = sessions[pin];
+    if (s.calledCount >= s.issuedCount) return;
+    s.calledCount += 1;
+    io.to(pin).emit('state_update', sessionState(pin));
+  });
+
+  socket.on('reset', () => {
+    if (!pin || !sessions[pin]) return;
+    sessions[pin] = { issuedCount: 0, calledCount: 0 };
+    io.to(pin).emit('state_update', sessionState(pin));
+    io.to(pin).emit('reset_done');
+  });
+});
+
+const PORT = process.env.PORT || 3000;
+server.listen(PORT, '0.0.0.0', () => {
+  console.log(`Queue server running on port ${PORT}`);
+});