diff --git a/server.js b/server.js
new file mode 100644
index 0000000..3b902c6
--- /dev/null
+++ b/server.js
@@ -0,0 +1,425 @@
+const express = require('express');
+const session = require('express-session');
+const bcrypt = require('bcryptjs');
+const multer = require('multer');
+const rateLimit = require('express-rate-limit');
+const crypto = require('crypto');
+const fs = require('fs');
+const path = require('path');
+
+const PORT = process.env.PORT || 3210;
+// 127.0.0.1 by default: on a VPS, Nginx fronts this with TLS and is the only
+// thing that should be reachable from outside. On the old local-Windows setup
+// this was 0.0.0.0 for LAN access; set HOST=0.0.0.0 explicitly if you still
+// need that. COOKIE_SECURE should be "true" once you're behind real HTTPS.
+const HOST = process.env.HOST || '127.0.0.1';
+const COOKIE_SECURE = process.env.COOKIE_SECURE === 'true';
+const DATA_FILE = path.join(__dirname, 'data.json');
+const PID_FILE = path.join(__dirname, 'server.pid');
+const FRONTEND_DIST = path.join(__dirname, '..', 'frontend', 'dist');
+const UPLOADS_DIR = path.join(__dirname, 'uploads');
+const AUTH_FILE = path.join(__dirname, 'auth.json');
+const DEFAULT_USERNAME = 'admin';
+const DEFAULT_PASSWORD = 'admin123';
+
+if (!fs.existsSync(UPLOADS_DIR)) fs.mkdirSync(UPLOADS_DIR, { recursive: true });
+
+/* --------------------------------- auth ---------------------------------- */
+
+function loadAuth() {
+  if (!fs.existsSync(AUTH_FILE)) {
+    const auth = { username: DEFAULT_USERNAME, passwordHash: bcrypt.hashSync(DEFAULT_PASSWORD, 10) };
+    fs.writeFileSync(AUTH_FILE, JSON.stringify(auth, null, 2), 'utf8');
+    return auth;
+  }
+  try {
+    return JSON.parse(fs.readFileSync(AUTH_FILE, 'utf8'));
+  } catch (e) {
+    const auth = { username: DEFAULT_USERNAME, passwordHash: bcrypt.hashSync(DEFAULT_PASSWORD, 10) };
+    fs.writeFileSync(AUTH_FILE, JSON.stringify(auth, null, 2), 'utf8');
+    return auth;
+  }
+}
+function saveAuth(auth) {
+  fs.writeFileSync(AUTH_FILE, JSON.stringify(auth, null, 2), 'utf8');
+}
+
+/* ------------------------------ secret / crypto -------------------------- */
+// Used to encrypt the DeepSeek API key (and anything else sensitive) at
+// rest, so it isn't sitting around the filesystem as plain text.
+
+const SECRET_KEY_FILE = path.join(__dirname, '.secret-key');
+function getSecretKey() {
+  if (!fs.existsSync(SECRET_KEY_FILE)) {
+    const key = crypto.randomBytes(32);
+    fs.writeFileSync(SECRET_KEY_FILE, key.toString('base64'), { encoding: 'utf8', mode: 0o600 });
+    return key;
+  }
+  return Buffer.from(fs.readFileSync(SECRET_KEY_FILE, 'utf8').trim(), 'base64');
+}
+const SECRET_KEY = getSecretKey();
+
+function encrypt(text) {
+  if (!text) return '';
+  const iv = crypto.randomBytes(12);
+  const cipher = crypto.createCipheriv('aes-256-gcm', SECRET_KEY, iv);
+  const encrypted = Buffer.concat([cipher.update(text, 'utf8'), cipher.final()]);
+  const tag = cipher.getAuthTag();
+  return Buffer.concat([iv, tag, encrypted]).toString('base64');
+}
+function decrypt(b64) {
+  if (!b64) return '';
+  try {
+    const buf = Buffer.from(b64, 'base64');
+    const iv = buf.subarray(0, 12);
+    const tag = buf.subarray(12, 28);
+    const encrypted = buf.subarray(28);
+    const decipher = crypto.createDecipheriv('aes-256-gcm', SECRET_KEY, iv);
+    decipher.setAuthTag(tag);
+    return Buffer.concat([decipher.update(encrypted), decipher.final()]).toString('utf8');
+  } catch (e) {
+    return '';
+  }
+}
+
+/* --------------------------------- AI config ------------------------------ */
+
+const AI_CONFIG_FILE = path.join(__dirname, 'ai-config.json');
+// Lets you point this at a different OpenAI-compatible endpoint if needed
+// (e.g. testing against a mock server); defaults to the real DeepSeek API.
+const DEEPSEEK_API_BASE = process.env.DEEPSEEK_API_BASE || 'https://api.deepseek.com';
+
+function loadAiConfig() {
+  try {
+    const raw = JSON.parse(fs.readFileSync(AI_CONFIG_FILE, 'utf8'));
+    return { apiKey: decrypt(raw.apiKeyEnc || '') };
+  } catch (e) {
+    return { apiKey: '' };
+  }
+}
+function saveAiConfig(apiKey) {
+  fs.writeFileSync(AI_CONFIG_FILE, JSON.stringify({ apiKeyEnc: encrypt(apiKey) }, null, 2), 'utf8');
+}
+
+const REGION_LABELS = {
+  africa: 'Africa', middle_east: 'Middle East', australia: 'Australia/Oceania',
+  europe: 'Europe', sea: 'Southeast Asia', other: 'Other',
+};
+
+function buildCustomerContext(c) {
+  const lines = [];
+  lines.push(`Company: ${c.company || '(unknown / not on file)'}`);
+  if (c.contact) lines.push(`Contact person: ${c.contact}`);
+  const place = [c.country, REGION_LABELS[c.region]].filter(Boolean).join(', ');
+  if (place) lines.push(`Location: ${place}`);
+  if (c.productLines && c.productLines.length) lines.push(`Product interest: ${c.productLines.join(', ')}`);
+  if (c.intendedModel || c.intendedQty) {
+    lines.push(`Specific model interest: ${c.intendedModel || '(model unspecified)'}${c.intendedQty ? `, quantity: ${c.intendedQty}` : ''}`);
+  }
+  if (c.lastContact) lines.push(`Last contact date: ${c.lastContact}`);
+  if (c.notes) lines.push(`Background research on this customer: ${c.notes}`);
+  if (c.tags) lines.push(`Additional remarks: ${c.tags}`);
+  if (c.isVip) lines.push('This is a VIP / priority customer — extra attentive tone.');
+  if (c.hasOrdered) lines.push('This customer has already placed an order before — this follow-up is with an existing buyer, not a cold lead.');
+  return lines.join('\n');
+}
+
+async function callDeepSeek(apiKey, messages) {
+  const resp = await fetch(`${DEEPSEEK_API_BASE}/chat/completions`, {
+    method: 'POST',
+    headers: {
+      'Content-Type': 'application/json',
+      Authorization: `Bearer ${apiKey}`,
+    },
+    body: JSON.stringify({
+      model: 'deepseek-v4-flash',
+      messages,
+      temperature: 0.7,
+      max_tokens: 600,
+    }),
+  });
+  if (!resp.ok) {
+    const errText = await resp.text().catch(() => '');
+    throw new Error(`DeepSeek API error ${resp.status}: ${errText.slice(0, 200)}`);
+  }
+  const data = await resp.json();
+  const content = data.choices && data.choices[0] && data.choices[0].message && data.choices[0].message.content;
+  if (!content) throw new Error('DeepSeek API returned an empty response');
+  return content;
+}
+
+/* ------------------------------ data file ------------------------------ */
+
+function readData() {
+  try {
+    return JSON.parse(fs.readFileSync(DATA_FILE, 'utf8'));
+  } catch (e) {
+    return {};
+  }
+}
+
+function writeData(data) {
+  // write to a temp file then rename, avoids corrupting data.json if the
+  // process is killed mid-write
+  const tmp = DATA_FILE + '.tmp';
+  fs.writeFileSync(tmp, JSON.stringify(data, null, 2), 'utf8');
+  fs.renameSync(tmp, DATA_FILE);
+}
+
+// only allow simple ids (our customer ids are like "c_169..._ab12c"),
+// this keeps the upload path from ever escaping the uploads/ folder
+function safeId(id) {
+  return /^[A-Za-z0-9_-]+$/.test(id) ? id : null;
+}
+
+/* --------------------------------- app ---------------------------------- */
+
+const app = express();
+
+// behind Nginx, Express needs this to read X-Forwarded-* correctly —
+// otherwise req.ip is always Nginx's own address (breaks rate limiting)
+// and the "secure" cookie flag can't tell the request was HTTPS.
+app.set('trust proxy', 1);
+
+app.use(express.json({ limit: '10mb' }));
+app.use(session({
+  secret: crypto.randomBytes(32).toString('hex'),
+  resave: false,
+  saveUninitialized: false,
+  cookie: {
+    httpOnly: true,
+    sameSite: 'lax',
+    secure: COOKIE_SECURE,
+    maxAge: 30 * 24 * 60 * 60 * 1000, // 30 days
+  },
+}));
+
+function requireAuth(req, res, next) {
+  if (req.session && req.session.authed) return next();
+  res.status(401).json({ error: 'not authenticated' });
+}
+
+const loginLimiter = rateLimit({
+  windowMs: 15 * 60 * 1000,
+  max: 5,
+  standardHeaders: true,
+  legacyHeaders: false,
+  message: { error: 'too many login attempts, please try again in a few minutes' },
+});
+
+/* -------------------------------- auth api ------------------------------- */
+
+app.post('/api/auth/login', loginLimiter, (req, res) => {
+  const body = req.body || {};
+  const username = body.username || '';
+  const password = body.password || '';
+  const auth = loadAuth();
+  if (username === auth.username && bcrypt.compareSync(password, auth.passwordHash)) {
+    req.session.authed = true;
+    req.session.username = username;
+    return res.json({ ok: true, username });
+  }
+  res.status(401).json({ error: 'invalid credentials' });
+});
+
+app.post('/api/auth/logout', (req, res) => {
+  if (req.session) {
+    req.session.destroy(() => res.json({ ok: true }));
+  } else {
+    res.json({ ok: true });
+  }
+});
+
+app.get('/api/auth/check', (req, res) => {
+  const authed = !!(req.session && req.session.authed);
+  res.json({ authed, username: authed ? req.session.username : null });
+});
+
+app.post('/api/auth/change-password', requireAuth, (req, res) => {
+  const body = req.body || {};
+  const currentPassword = body.currentPassword || '';
+  const newPassword = body.newPassword || '';
+  const auth = loadAuth();
+  if (!bcrypt.compareSync(currentPassword, auth.passwordHash)) {
+    return res.status(400).json({ error: 'current password is incorrect' });
+  }
+  if (newPassword.length < 4) {
+    return res.status(400).json({ error: 'new password is too short' });
+  }
+  auth.passwordHash = bcrypt.hashSync(newPassword, 10);
+  saveAuth(auth);
+  res.json({ ok: true });
+});
+
+/* ------------------------------ storage api ------------------------------ */
+
+app.get('/api/storage/:key', requireAuth, (req, res) => {
+  const data = readData();
+  const key = req.params.key;
+  if (!(key in data)) return res.status(404).json({ error: 'not found' });
+  res.json({ value: data[key] });
+});
+
+app.put('/api/storage/:key', requireAuth, (req, res) => {
+  const data = readData();
+  data[req.params.key] = req.body.value;
+  writeData(data);
+  res.json({ ok: true });
+});
+
+/* --------------------------------- ai api --------------------------------- */
+
+app.get('/api/ai-config', requireAuth, (req, res) => {
+  const cfg = loadAiConfig();
+  res.json({ hasKey: !!cfg.apiKey });
+});
+
+app.put('/api/ai-config', requireAuth, (req, res) => {
+  const apiKey = ((req.body && req.body.apiKey) || '').trim();
+  if (!apiKey) return res.status(400).json({ error: 'apiKey is required' });
+  saveAiConfig(apiKey);
+  res.json({ ok: true });
+});
+
+app.delete('/api/ai-config', requireAuth, (req, res) => {
+  try { fs.unlinkSync(AI_CONFIG_FILE); } catch (e) {}
+  res.json({ ok: true });
+});
+
+app.post('/api/ai-config/test', requireAuth, async (req, res) => {
+  const cfg = loadAiConfig();
+  if (!cfg.apiKey) return res.status(400).json({ error: 'no API key configured' });
+  try {
+    const content = await callDeepSeek(cfg.apiKey, [{ role: 'user', content: 'Reply with exactly: OK' }]);
+    res.json({ ok: true, reply: content.trim() });
+  } catch (e) {
+    res.status(400).json({ error: e.message });
+  }
+});
+
+const aiLimiter = rateLimit({
+  windowMs: 10 * 60 * 1000,
+  max: 30,
+  standardHeaders: true,
+  legacyHeaders: false,
+  message: { error: 'too many AI requests, please slow down' },
+});
+
+app.post('/api/ai/draft', requireAuth, aiLimiter, async (req, res) => {
+  const body = req.body || {};
+  const customerId = body.customerId;
+  const channel = body.channel;
+  if (!customerId || !['email', 'whatsapp'].includes(channel)) {
+    return res.status(400).json({ error: 'invalid request' });
+  }
+  const cfg = loadAiConfig();
+  if (!cfg.apiKey) return res.status(400).json({ error: 'DeepSeek API key not configured' });
+
+  const data = readData();
+  let customers = [];
+  try { customers = JSON.parse(data['crm:customers'] || '[]'); } catch (e) {}
+  const customer = customers.find((c) => c.id === customerId);
+  if (!customer) return res.status(404).json({ error: 'customer not found' });
+
+  const context = buildCustomerContext(customer);
+  const systemPrompt = 'You are a sales assistant helping a B2B export salesperson at a Chinese power-equipment company (UPS systems, rectifiers, solar inverters, battery storage) write natural, professional follow-up outreach to overseas customers. Always write in English. Never sound like a generic template, reference specifics from the customer info given. Output only the requested content, with no meta-commentary, explanations, or markdown formatting.';
+
+  const userPrompt = channel === 'email'
+    ? `Customer info:\n${context}\n\nWrite a short, warm but professional follow-up email to this customer. Respond in EXACTLY this format with no extra text:\nSUBJECT: <subject line>\nBODY:\n<email body, 3-5 short paragraphs max, sign off with "[Your name]">`
+    : `Customer info:\n${context}\n\nWrite a short, casual WhatsApp message to check in with this customer (2-4 sentences, friendly tone, no formal greeting like "Dear", a light emoji is fine if it feels natural). Respond with ONLY the message text, nothing else.`;
+
+  try {
+    const content = await callDeepSeek(cfg.apiKey, [
+      { role: 'system', content: systemPrompt },
+      { role: 'user', content: userPrompt },
+    ]);
+    if (channel === 'email') {
+      const subjectMatch = content.match(/SUBJECT:\s*(.+)/i);
+      const bodyMatch = content.match(/BODY:\s*([\s\S]*)/i);
+      res.json({
+        subject: subjectMatch ? subjectMatch[1].trim() : 'Following up',
+        body: bodyMatch ? bodyMatch[1].trim() : content.trim(),
+      });
+    } else {
+      res.json({ body: content.trim() });
+    }
+  } catch (e) {
+    res.status(502).json({ error: e.message });
+  }
+});
+
+/* ------------------------- communication attachments ------------------------- */
+
+const upload = multer({
+  storage: multer.diskStorage({
+    destination: (req, file, cb) => {
+      const cid = safeId(req.params.customerId);
+      if (!cid) return cb(new Error('invalid customer id'));
+      const dir = path.join(UPLOADS_DIR, cid);
+      fs.mkdirSync(dir, { recursive: true });
+      cb(null, dir);
+    },
+    filename: (req, file, cb) => {
+      const ts = Date.now();
+      const rand = Math.random().toString(36).slice(2, 8);
+      const ext = path.extname(file.originalname).slice(0, 10);
+      cb(null, `${ts}_${rand}${ext}`);
+    },
+  }),
+  limits: { fileSize: 25 * 1024 * 1024 }, // 25MB per file
+});
+
+app.post('/api/uploads/:customerId', requireAuth, (req, res) => {
+  if (!safeId(req.params.customerId)) return res.status(400).json({ error: 'invalid customer id' });
+  upload.single('file')(req, res, (err) => {
+    if (err) return res.status(400).json({ error: err.message });
+    if (!req.file) return res.status(400).json({ error: 'no file received' });
+    // multer/busboy 默认按 latin1 解析 multipart 里的文件名字段（这是老版HTTP规范的行为），
+    // 但浏览器实际发送的中文文件名是 UTF-8 字节，所以这里要把它从 latin1 转回 UTF-8，
+    // 不然中文文件名会变成乱码存进 data.json。
+    const originalName = Buffer.from(req.file.originalname, 'latin1').toString('utf8');
+    res.json({ fileName: req.file.filename, originalName, size: req.file.size });
+  });
+});
+
+app.delete('/api/uploads/:customerId/:fileName', requireAuth, (req, res) => {
+  const cid = safeId(req.params.customerId);
+  const fname = req.params.fileName;
+  const isSafeFile = fname && !fname.includes('..') && !fname.includes('/') && !fname.includes('\\');
+  if (!cid || !isSafeFile) return res.status(400).json({ error: 'invalid request' });
+  fs.unlink(path.join(UPLOADS_DIR, cid, fname), () => {
+    // a missing file is also treated as success, so clicking delete twice never errors
+    res.json({ ok: true });
+  });
+});
+
+app.use('/uploads', requireAuth, express.static(UPLOADS_DIR));
+
+app.use(express.static(FRONTEND_DIST));
+app.get('*', (req, res) => {
+  res.sendFile(path.join(FRONTEND_DIST, 'index.html'));
+});
+
+/* ------------------------------- bootstrap ------------------------------ */
+
+loadAuth(); // make sure auth.json exists with default credentials on first run
+
+fs.writeFileSync(PID_FILE, String(process.pid), 'utf8');
+process.on('exit', () => {
+  try { fs.unlinkSync(PID_FILE); } catch (e) {}
+});
+process.on('SIGINT', () => process.exit(0));
+process.on('SIGTERM', () => process.exit(0));
+
+const server = app.listen(PORT, HOST, () => {
+  console.log(`[customer-crm] running at http://${HOST}:${PORT}`);
+});
+
+server.on('error', (e) => {
+  if (e.code === 'EADDRINUSE') {
+    console.log('[customer-crm] another instance is already running on this port, exiting.');
+    try { fs.unlinkSync(PID_FILE); } catch (err) {}
+    process.exit(0);
+  }
+  throw e;
+});