♻️ refactor(codebase): 拆分大文件并收敛模块职责

- 拆分 ConnectionModal、DataGrid、QueryEditor、App 等前端大文件

- 抽出 driver assets、v2 workbench 样式和 source-as-test 读取辅助

- 更新相关测试以覆盖拆分后的源码位置

frontend/src/test/readV2ThemeCss.ts

@@ -0,0 +1,6 @@
+import { readFileSync } from 'node:fs';
+
+export const readV2ThemeCss = (): string => [
+  readFileSync(new URL('../v2-theme.css', import.meta.url), 'utf8'),
+  readFileSync(new URL('../styles/v2-theme-workbench.css', import.meta.url), 'utf8'),
+].join('\n');