feat: add Service API file preview endpoint (#23534)

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

web/app/components/develop/template/template_workflow.en.mdx

@@ -747,6 +747,86 @@ Workflow applications offers non-session support and is ideal for translation, a
 
 ---
 
+<Heading
+  url='/files/:file_id/preview'
+  method='GET'
+  title='File Preview'
+  name='#file-preview'
+/>
+<Row>
+  <Col>
+    Preview or download uploaded files. This endpoint allows you to access files that have been previously uploaded via the File Upload API.
+    
+    <i>Files can only be accessed if they belong to messages within the requesting application.</i>
+
+    ### Path Parameters
+    - `file_id` (string) Required
+      The unique identifier of the file to preview, obtained from the File Upload API response.
+
+    ### Query Parameters
+    - `as_attachment` (boolean) Optional
+      Whether to force download the file as an attachment. Default is `false` (preview in browser).
+
+    ### Response
+    Returns the file content with appropriate headers for browser display or download.
+    - `Content-Type` Set based on file mime type
+    - `Content-Length` File size in bytes (if available)
+    - `Content-Disposition` Set to "attachment" if `as_attachment=true`
+    - `Cache-Control` Caching headers for performance
+    - `Accept-Ranges` Set to "bytes" for audio/video files
+
+    ### Errors
+    - 400, `invalid_param`, abnormal parameter input
+    - 403, `file_access_denied`, file access denied or file does not belong to current application
+    - 404, `file_not_found`, file not found or has been deleted
+    - 500, internal server error
+
+  </Col>
+  <Col sticky>
+    ### Request Example
+    <CodeGroup title="Request" tag="GET" label="/files/:file_id/preview" targetCode={`curl -X GET '${props.appDetail.api_base_url}/files/72fa9618-8f89-4a37-9b33-7e1178a24a67/preview' \\\n--header 'Authorization: Bearer {api_key}'`}>
+
+    ```bash {{ title: 'cURL' }}
+    curl -X GET '${props.appDetail.api_base_url}/files/72fa9618-8f89-4a37-9b33-7e1178a24a67/preview' \
+    --header 'Authorization: Bearer {api_key}'
+    ```
+
+    </CodeGroup>
+
+    ### Download as Attachment
+    <CodeGroup title="Download Request" tag="GET" label="/files/:file_id/preview?as_attachment=true" targetCode={`curl -X GET '${props.appDetail.api_base_url}/files/72fa9618-8f89-4a37-9b33-7e1178a24a67/preview?as_attachment=true' \\\n--header 'Authorization: Bearer {api_key}' \\\n--output downloaded_file.png`}>
+
+    ```bash {{ title: 'cURL' }}
+    curl -X GET '${props.appDetail.api_base_url}/files/72fa9618-8f89-4a37-9b33-7e1178a24a67/preview?as_attachment=true' \
+    --header 'Authorization: Bearer {api_key}' \
+    --output downloaded_file.png
+    ```
+
+    </CodeGroup>
+
+    ### Response Headers Example
+    <CodeGroup title="Response Headers">
+    ```http {{ title: 'Headers - Image Preview' }}
+    Content-Type: image/png
+    Content-Length: 1024
+    Cache-Control: public, max-age=3600
+    ```
+    </CodeGroup>
+
+    ### Download Response Headers
+    <CodeGroup title="Download Response Headers">
+    ```http {{ title: 'Headers - File Download' }}
+    Content-Type: image/png
+    Content-Length: 1024
+    Content-Disposition: attachment; filename*=UTF-8''example.png
+    Cache-Control: public, max-age=3600
+    ```
+    </CodeGroup>
+  </Col>
+</Row>
+
+---
+
 <Heading
   url='/workflows/logs'
   method='GET'