feat: 小菜记账 v1.0 - 完整功能实现

核心功能：
- 记账CRUD（支出/收入/分类/备注/日期）
- 统计分析（概览/分类占比/每日趋势）
- 预算管理（按月设置/进度条/超支提醒）
- 数据导出CSV

安全与认证：
- HMAC-SHA256签名token认证
- 用户数据隔离
- 输入验证与错误处理
- CORS配置

前端优化：
- 骨架屏加载
- 账单按日期分组
- 预算页面重构（快捷预设+Numpad）
- SvgIcon组件（H5+微信双端适配）
- 下拉刷新

后端优化：
- 共享日期工具函数
- 数据库连接池优化
- 健康检查端点
- 优雅关闭处理

技术栈：
- 前端：Uni-app (Vue 3 + Pinia)
- 后端：Node.js + Express + MySQL

server/src/routes/stats.ts

@@ -0,0 +1,91 @@
+import { Router, Response } from 'express'
+import pool from '../db/connection'
+import { AuthRequest } from '../middleware/auth'
+import { getCurrentMonth, getMonthRange } from '../utils/date'
+
+const router = Router()
+
+router.get('/overview', async (req: AuthRequest, res: Response) => {
+  try {
+    const { month } = req.query
+    const m = (month as string) || getCurrentMonth()
+    const range = getMonthRange(m)
+    if (!range) return res.status(400).json({ code: 40001, message: '月份格式无效' })
+    const { startDate, endDate } = range
+
+    const [rows] = await pool.query(
+      `SELECT
+        COALESCE(SUM(CASE WHEN type = 'expense' THEN amount ELSE 0 END), 0) as expense,
+        COALESCE(SUM(CASE WHEN type = 'income' THEN amount ELSE 0 END), 0) as income,
+        COUNT(*) as count
+       FROM transactions WHERE user_id = ? AND date >= ? AND date <= ?`,
+      [req.userId, startDate, endDate]
+    )
+    const row = (rows as any[])[0]
+
+    const now = new Date()
+    const [year, mon] = m.split('-').map(Number)
+    const isCurrentMonth = year === now.getFullYear() && mon === now.getMonth() + 1
+    const elapsedDays = isCurrentMonth ? now.getDate() : new Date(year, mon, 0).getDate()
+    const daily = elapsedDays > 0 ? Math.round(row.expense / elapsedDays) : 0
+
+    res.json({
+      code: 0,
+      data: { expense: row.expense, income: row.income, count: row.count, daily }
+    })
+  } catch (err) {
+    console.error('[Stats] overview error:', err)
+    res.status(500).json({ code: 50000, message: '服务器错误' })
+  }
+})
+
+router.get('/category', async (req: AuthRequest, res: Response) => {
+  try {
+    const { month, type = 'expense' } = req.query
+    const m = (month as string) || getCurrentMonth()
+    const range = getMonthRange(m)
+    if (!range) return res.status(400).json({ code: 40001, message: '月份格式无效' })
+    const { startDate, endDate } = range
+
+    const [rows] = await pool.query(
+      `SELECT c.id, COALESCE(c.name, '未分类') as name, COALESCE(c.icon, '?') as icon, COALESCE(c.color, '#BFB3B3') as color, SUM(t.amount) as amount, COUNT(t.id) as count
+       FROM transactions t
+       LEFT JOIN categories c ON t.category_id = c.id
+       WHERE t.user_id = ? AND t.type = ? AND t.date >= ? AND t.date <= ?
+       GROUP BY c.id
+       ORDER BY amount DESC`,
+      [req.userId, type, startDate, endDate]
+    )
+
+    res.json({ code: 0, data: rows })
+  } catch (err) {
+    console.error('[Stats] category error:', err)
+    res.status(500).json({ code: 50000, message: '服务器错误' })
+  }
+})
+
+router.get('/trend', async (req: AuthRequest, res: Response) => {
+  try {
+    const { month, type = 'expense' } = req.query
+    const m = (month as string) || getCurrentMonth()
+    const range = getMonthRange(m)
+    if (!range) return res.status(400).json({ code: 40001, message: '月份格式无效' })
+    const { startDate, endDate } = range
+
+    const [rows] = await pool.query(
+      `SELECT date, SUM(amount) as amount
+       FROM transactions
+       WHERE user_id = ? AND type = ? AND date >= ? AND date <= ?
+       GROUP BY date
+       ORDER BY date`,
+      [req.userId, type, startDate, endDate]
+    )
+
+    res.json({ code: 0, data: rows })
+  } catch (err) {
+    console.error('[Stats] trend error:', err)
+    res.status(500).json({ code: 50000, message: '服务器错误' })
+  }
+})
+
+export default router