refactor(JsonTools): 规范化页面组件目录结构

- 将子组件移至 components/ 子目录（JsonDiffInput、DiffResult、JsonFormatSection、JsonConvertSection、DiffNavigator、JsonTree）
- 将 diffEngine.ts 工具函数移至 src/utils/
- 提取 ConvertFunction/ConvertResult 类型到 types.ts，解决循环依赖
- 创建 __tests__/ 目录结构
- 更新所有相关导入路径

Co-authored-by: Cursor <cursoragent@cursor.com>

src/utils/__tests__/diffEngine.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect } from 'vitest';
-import { diffJson } from '../../pages/JsonTools/diffEngine';
+import { diffJson } from '../diffEngine';
 
 describe('diffJson', () => {
   it('should detect added property', () => {