feat(web): enhance knowledge base sharing with stop share feedback

- Fix file download URL to use absolute API path instead of apiPrefix variable
- Add stopShareSuccess i18n message for English locale
- Add stopShareSuccess i18n message for Chinese locale
- Update ShareModal to display different success messages based on share toggle state
- Show "Sharing is off" message when disabling knowledge base sharing
- Improve user feedback when toggling share status on/off

web/src/api/knowledgeBase.ts

@@ -154,7 +154,7 @@ export const uploadFile = async (data: FormData, options?: UploadFileOptions) =>
 // 下载文件
 export const downloadFile = async (fileId: string, fileName?: string) => {
   const token = cookieUtils.get('authToken');
-  const url = `${apiPrefix}/files/${fileId}`;
+  const url = `/api/files/${fileId}`;
   
   try {
     const response = await fetch(url, {