Fix SFTP file upload failures with JWT filer tokens (#8448)

* Fix SFTP file upload failures with JWT filer tokens (issue #8425)

When JWT authentication is enabled for filer operations via jwt.filer_signing.*
configuration, SFTP server file upload requests were rejected because they lacked
JWT authorization headers.

Changes:
- Added JWT signing key and expiration fields to SftpServer struct
- Modified putFile() to generate and include JWT tokens in upload requests
- Enhanced SFTPServiceOptions with JWT configuration fields
- Updated SFTP command startup to load and pass JWT config to service

This allows SFTP uploads to authenticate with JWT-enabled filers, consistent
with how other SeaweedFS components (S3 API, file browser) handle filer auth.

Fixes #8425

* Apply suggestion from @gemini-code-assist[bot]

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

---------

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

weed/sftpd/sftp_filer.go

@@ -17,6 +17,7 @@ import (
 	"github.com/seaweedfs/seaweedfs/weed/glog"
 	"github.com/seaweedfs/seaweedfs/weed/pb"
 	filer_pb "github.com/seaweedfs/seaweedfs/weed/pb/filer_pb"
+	"github.com/seaweedfs/seaweedfs/weed/security"
 	weed_server "github.com/seaweedfs/seaweedfs/weed/server"
 	"github.com/seaweedfs/seaweedfs/weed/sftpd/user"
 	"github.com/seaweedfs/seaweedfs/weed/util"
@@ -333,6 +334,14 @@ func (fs *SftpServer) putFile(filepath string, reader io.Reader, user *user.User
 	}
 	req.Header.Set("Content-Type", "application/octet-stream")
 
+	// Add JWT authorization if filer signing key is configured
+	if len(fs.filerSigningKey) > 0 {
+		jwt := security.GenJwtForFilerServer(security.SigningKey(fs.filerSigningKey), fs.filerSigningExpiresAfter)
+		if jwt != "" {
+			req.Header.Set("Authorization", "Bearer "+string(jwt))
+		}
+	}
+
 	resp, err := http.DefaultClient.Do(req)
 	if err != nil {
 		return fmt.Errorf("upload to filer: %w", err)