Initial commit: Markdown editor with file management and regex tools

项目特性：
- 完整的Markdown编辑器，支持实时预览
- 文件管理功能，支持保存/加载/删除文件
- 正则表达式工具，支持批量文本替换
- 前后端分离架构
- 响应式设计

技术栈：
- 前端：React + TypeScript + Vite
- 后端：Python Flask
- Markdown解析：Python-Markdown

包含组件：
- WorkingMarkdownEditor: 基础功能版本
- FullMarkdownEditor: 完整功能版本
- SimpleMarkdownEditor: 简化版本

frontend/src/utils/markdown.ts

@@ -0,0 +1,111 @@
+/**
+ * Markdown工具模块
+ * 提供Markdown相关的辅助函数
+ */
+
+/**
+ * 提取Markdown中的标题用于目录
+ */
+export function extractHeadings(content: string): Array<{
+  level: number;
+  text: string;
+  id: string;
+}> {
+  const headingRegex = /^(#{1,6})\s+(.+)$/gm;
+  const headings: Array<{ level: number; text: string; id: string }> = [];
+  let match;
+
+  while ((match = headingRegex.exec(content)) !== null) {
+    const level = match[1].length;
+    const text = match[2].trim();
+    const id = text.toLowerCase().replace(/[^\w\u4e00-\u9fa5]+/g, '-');
+
+    headings.push({ level, text, id });
+  }
+
+  return headings;
+}
+
+/**
+ * 计算阅读时间
+ */
+export function calculateReadingTime(content: string): number {
+  const chineseChars = content.match(/[\u4e00-\u9fa5]/g) || [];
+  const englishWords = content.match(/\b\w+\b/g) || [];
+
+  const chineseTime = chineseChars.length / 500;
+  const englishTime = englishWords.length / 200;
+
+  return Math.max(1, Math.ceil(chineseTime + englishTime));
+}
+
+/**
+ * 计算字数统计
+ */
+export function calculateWordCount(content: string): {
+  characters: number;
+  words: number;
+  lines: number;
+} {
+  const chineseChars = content.match(/[\u4e00-\u9fa5]/g) || [];
+  const englishWords = content.match(/\b\w+\b/g) || [];
+  const lines = content.split('\n').length;
+
+  return {
+    characters: chineseChars.length,
+    words: englishWords.length,
+    lines,
+  };
+}
+
+/**
+ * 自动保存到本地存储
+ */
+export function saveToLocalStorage(key: string, content: string): void {
+  try {
+    localStorage.setItem(`markdown-editor-${key}`, content);
+  } catch (error) {
+    console.warn('Failed to save to localStorage:', error);
+  }
+}
+
+/**
+ * 从本地存储加载内容
+ */
+export function loadFromLocalStorage(key: string): string | null {
+  try {
+    return localStorage.getItem(`markdown-editor-${key}`);
+  } catch (error) {
+    console.warn('Failed to load from localStorage:', error);
+    return null;
+  }
+}
+
+/**
+ * 格式化文件大小
+ */
+export function formatFileSize(bytes: number): string {
+  if (bytes === 0) return '0 B';
+
+  const k = 1024;
+  const sizes = ['B', 'KB', 'MB', 'GB'];
+  const i = Math.floor(Math.log(bytes) / Math.log(k));
+
+  return `${parseFloat((bytes / Math.pow(k, i)).toFixed(2))} ${sizes[i]}`;
+}
+
+/**
+ * 格式化时间戳
+ */
+export function formatDate(timestamp: number): string {
+  const date = new Date(timestamp);
+  const now = new Date();
+  const diff = now.getTime() - date.getTime();
+
+  if (diff < 60000) return '刚刚';
+  if (diff < 3600000) return `${Math.floor(diff / 60000)}分钟前`;
+  if (diff < 86400000) return `${Math.floor(diff / 3600000)}小时前`;
+  if (diff < 604800000) return `${Math.floor(diff / 86400000)}天前`;
+
+  return date.toLocaleDateString('zh-CN');
+}