feat: add i18n support for initialization page and fix plugin loading text

- Add language selector to register/initialization page with Chinese and English options
- Add register section translations to both zh-Hans.ts and en-US.ts
- Replace hardcoded Chinese texts in register page with i18n translation calls
- Fix hardcoded '加载中...' text in plugin configuration dialog to use t('plugins.loading')
- Follow existing login page pattern for language selector implementation
- Maintain consistent UI/UX design with proper language switching functionality

Co-Authored-By: Junyan Qin <Chin>, 秦骏言 in Chinese, you can call me my english name Rock Chin. <rockchinq@gmail.com>

web/src/app/home/plugins/plugin-installed/plugin-form/PluginForm.tsx

@@ -72,7 +72,7 @@ export default function PluginForm({
   };
 
   if (!pluginInfo || !pluginConfig) {
-    return <div>加载中...</div>;
+    return <div>{t('plugins.loading')}</div>;
   }
 
   function deletePlugin() {