docs: 添加中文文档，新增前端和后端代码

- 新增 README_CN.md 中文文档
- 新增 frontend/ Vue 3 前端项目
- 新增 web/ FastAPI 后端项目

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

frontend/.editorconfig

@@ -0,0 +1,8 @@
+[*.{js,jsx,mjs,cjs,ts,tsx,mts,cts,vue,css,scss,sass,less,styl}]
+charset = utf-8
+indent_size = 2
+indent_style = space
+insert_final_newline = true
+trim_trailing_whitespace = true
+end_of_line = lf
+max_line_length = 100