refactor: 系统优化 - 错误处理、输入验证、无限滚动

主要改进:
- 新增配置管理 (server/config.js)
- 新增日志工具 (server/utils/logger.js)
- 添加全局错误处理中间件，统一错误响应格式
- 添加输入验证和 AppError 错误类
- 重构 db.js 迁移逻辑，代码更清晰
- 前端列表改为无限滚动加载，每页 20 条
- 封装 AppState 状态管理模块

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

server/utils/helpers.js

@@ -1,4 +1,17 @@
-// 日期范围辅助函数
+/**
+ * 应用错误类
+ */
+class AppError extends Error {
+  constructor(message, status = 400) {
+    super(message);
+    this.status = status;
+    this.expose = true; // 允许向客户端暴露错误信息
+  }
+}
+
+/**
+ * 日期范围辅助函数
+ */
 function getMonthRange(qYear, qMonth) {
   const now = new Date();
   const y = Number(qYear) || now.getFullYear();
@@ -10,7 +23,9 @@ function getMonthRange(qYear, qMonth) {
   return { startDate, endDate };
 }
 
-// CSV行解析（处理引号内的逗号）
+/**
+ * CSV行解析（处理引号内的逗号）
+ */
 function parseCSVLine(line) {
   const result = [];
   let current = '';
@@ -31,4 +46,53 @@ function parseCSVLine(line) {
   return result;
 }
 
-module.exports = { getMonthRange, parseCSVLine };
+/**
+ * 输入验证函数
+ */
+function validateRequired(obj, fields) {
+  const missing = fields.filter(f => obj[f] === undefined || obj[f] === null || obj[f] === '');
+  if (missing.length > 0) {
+    throw new AppError(`缺少必填字段: ${missing.join(', ')}`, 400);
+  }
+}
+
+function validateNumber(value, field, min, max) {
+  const num = Number(value);
+  if (isNaN(num)) {
+    throw new AppError(`${field} 必须是数字`, 400);
+  }
+  if (min !== undefined && num < min) {
+    throw new AppError(`${field} 不能小于 ${min}`, 400);
+  }
+  if (max !== undefined && num > max) {
+    throw new AppError(`${field} 不能大于 ${max}`, 400);
+  }
+  return num;
+}
+
+function validateString(value, field, maxLength) {
+  if (typeof value !== 'string') {
+    throw new AppError(`${field} 必须是字符串`, 400);
+  }
+  if (maxLength && value.length > maxLength) {
+    throw new AppError(`${field} 长度不能超过 ${maxLength}`, 400);
+  }
+  return value.trim();
+}
+
+function validateInList(value, field, list) {
+  if (!list.includes(value)) {
+    throw new AppError(`${field} 值无效`, 400);
+  }
+  return value;
+}
+
+module.exports = {
+  AppError,
+  getMonthRange,
+  parseCSVLine,
+  validateRequired,
+  validateNumber,
+  validateString,
+  validateInList
+};

server/utils/logger.js

@@ -0,0 +1,79 @@
+/**
+ * 简单日志工具
+ * 支持日志级别和格式化输出
+ */
+
+const config = require('../config');
+
+const LEVELS = {
+  debug: 0,
+  info: 1,
+  warn: 2,
+  error: 3
+};
+
+const COLORS = {
+  debug: '\x1b[36m',   // cyan
+  info: '\x1b[32m',    // green
+  warn: '\x1b[33m',    // yellow
+  error: '\x1b[31m',   // red
+  reset: '\x1b[0m'
+};
+
+const currentLevel = LEVELS[config.log.level] || LEVELS.info;
+const colorize = config.log.colorize && process.stdout.isTTY;
+
+function formatTime() {
+  const d = new Date();
+  return d.toISOString().replace('T', ' ').slice(0, 19);
+}
+
+function formatMessage(level, ...args) {
+  const timestamp = formatTime();
+  const prefix = `[${timestamp}] [${level.toUpperCase()}]`;
+
+  if (colorize) {
+    return `${COLORS[level]}${prefix}${COLORS.reset} ${args.join(' ')}`;
+  }
+  return `${prefix} ${args.join(' ')}`;
+}
+
+const logger = {
+  debug(...args) {
+    if (currentLevel <= LEVELS.debug) {
+      console.log(formatMessage('debug', ...args));
+    }
+  },
+
+  info(...args) {
+    if (currentLevel <= LEVELS.info) {
+      console.log(formatMessage('info', ...args));
+    }
+  },
+
+  warn(...args) {
+    if (currentLevel <= LEVELS.warn) {
+      console.warn(formatMessage('warn', ...args));
+    }
+  },
+
+  error(...args) {
+    if (currentLevel <= LEVELS.error) {
+      console.error(formatMessage('error', ...args));
+    }
+  },
+
+  // 请求日志中间件
+  requestLogger(req, res, next) {
+    const start = Date.now();
+    res.on('finish', () => {
+      const duration = Date.now() - start;
+      const status = res.statusCode;
+      const level = status >= 400 ? 'warn' : 'info';
+      logger[level](`${req.method} ${req.path} ${status} ${duration}ms`);
+    });
+    next();
+  }
+};
+
+module.exports = logger;