refactor: v2 重构 — 模块化拆分 + AI Prompt模板化 + 前端状态管理

P0 - AI交互层:
- ai/prompt.js: 模块化 Prompt 模板
- ai/validator.js: JSON Schema 校验 + normalize
- ai/client.js: DeepSeek API 封装
- 金额计算唯一化，时间格式归一化

P1 - 后端架构:
- routes/: auth/rooms/messages/purchases 独立路由
- middleware/auth.js: 认证授权中间件
- ws/index.js: WebSocket 连接管理
- db.js: 启用 foreign_keys
- server.js: 从588行精简到40行入口

P2 - 前端架构:
- public/css/style.css: CSS 独立
- public/js/store.js: 全局状态 Store
- public/js/{chat,ws,purchases,auth}.js: 功能模块拆分
- index.html: 纯 HTML 结构, v2.6

server/routes/messages.js

@@ -0,0 +1,70 @@
+// 消息路由 + AI 分析
+const express = require('express');
+const { authMiddleware } = require('../middleware/auth');
+const { broadcastToRoomExcludeSelf } = require('../ws');
+const { buildSystemPrompt } = require('../ai/prompt');
+const { validate, normalize } = require('../ai/validator');
+const { callDeepSeek } = require('../ai/client');
+const { getHistory, addToHistory, hasPendingAction, handleAIResult, executePendingAction } = require('../handlers');
+const db = require('../db');
+const { timestamp } = require('../utils');
+
+const router = express.Router();
+
+router.get('/:roomId/messages', authMiddleware, (req, res) => {
+  const msgs = db.prepare('SELECT * FROM messages WHERE room_id = ? ORDER BY id ASC').all(req.params.roomId);
+  res.json(msgs);
+});
+
+router.post('/:roomId/messages', authMiddleware, async (req, res) => {
+  const { text, attachments } = req.body;
+  console.log('📨 收到消息, text:', (text||'').substring(0,30), 'attachments:', JSON.stringify(attachments));
+  const roomId = req.params.roomId;
+  const username = req.user.username;
+  const now = timestamp();
+
+  const result = db.prepare('INSERT INTO messages (room_id, user, text, attachments, timestamp) VALUES (?,?,?,?,?)').run(
+    roomId, username, text || '', attachments ? JSON.stringify(attachments) : null, now
+  );
+  const msg = { id: result.lastInsertRowid, room_id: roomId, user: username, text: text || '', attachments: attachments || [], timestamp: now };
+
+  const lastMsg = db.prepare('SELECT text, timestamp FROM messages WHERE room_id = ? ORDER BY id DESC LIMIT 1').get(roomId);
+  broadcastToRoomExcludeSelf(roomId, username, {
+    type: 'new_message', message: msg,
+    room_preview: { room_id: roomId, last_message: lastMsg ? lastMsg.text : '', last_time: lastMsg ? lastMsg.timestamp : '' }
+  });
+  addToHistory(roomId, 'user', `${username}: ${text || '图片'}`);
+  res.json(msg);
+
+  if (text && text.trim() === '确认' && hasPendingAction(roomId, username)) {
+    executePendingAction(roomId, username);
+    return;
+  }
+
+  try {
+    const history = getHistory(roomId);
+    const historyMessages = history.map(e => ({ role: e.role, content: e.content }));
+    const aiResponse = await analyzeWithDeepSeek(text || '', historyMessages, username, req.user.isAdmin);
+    if (aiResponse && aiResponse.action !== 'ignore') {
+      handleAIResult(aiResponse, roomId, username, text || '', attachments || []);
+    }
+  } catch (e) { console.error('AI 分析失败:', e); }
+});
+
+async function analyzeWithDeepSeek(text, historyMessages, username, isAdmin) {
+  const systemPrompt = buildSystemPrompt(username, isAdmin);
+  const messages = [
+    { role: 'system', content: systemPrompt },
+    ...historyMessages.slice(-30),
+    { role: 'user', content: `${username}: ${text}` }
+  ];
+  const content = await callDeepSeek(messages, 0.1);
+  console.log('🤖 AI 返回:', content);
+  const parsed = JSON.parse(content.replace(/```json|```/g, '').trim());
+  normalize(parsed);
+  const v = validate(parsed);
+  if (!v.valid) console.warn('⚠️ AI 返回校验失败:', v.error);
+  return parsed;
+}
+
+module.exports = router;