server: add missing concurrentFileUploadLimit flags for server command

The server command was missing the initialization of concurrentFileUploadLimit
flags for both filer and S3, causing a nil pointer dereference when starting
the server in combined mode.

This adds:
- filer.concurrentFileUploadLimit flag to server command
- s3.concurrentUploadLimitMB flag to server command
- s3.concurrentFileUploadLimit flag to server command

Fixes the panic: runtime error: invalid memory address or nil pointer dereference
at filer.go:332

weed/command/server.go

@@ -123,6 +123,7 @@ func init() {
 	filerOptions.cipher = cmdServer.Flag.Bool("filer.encryptVolumeData", false, "encrypt data on volume servers")
 	filerOptions.saveToFilerLimit = cmdServer.Flag.Int("filer.saveToFilerLimit", 0, "Small files smaller than this limit can be cached in filer store.")
 	filerOptions.concurrentUploadLimitMB = cmdServer.Flag.Int("filer.concurrentUploadLimitMB", 64, "limit total concurrent upload size")
+	filerOptions.concurrentFileUploadLimit = cmdServer.Flag.Int("filer.concurrentFileUploadLimit", 0, "limit number of concurrent file uploads, 0 means unlimited")
 	filerOptions.localSocket = cmdServer.Flag.String("filer.localSocket", "", "default to /tmp/seaweedfs-filer-<port>.sock")
 	filerOptions.showUIDirectoryDelete = cmdServer.Flag.Bool("filer.ui.deleteDir", true, "enable filer UI show delete directory button")
 	filerOptions.downloadMaxMBps = cmdServer.Flag.Int("filer.downloadMaxMBps", 0, "download max speed for each download request, in MB per second")
@@ -168,6 +169,8 @@ func init() {
 	s3Options.localSocket = cmdServer.Flag.String("s3.localSocket", "", "default to /tmp/seaweedfs-s3-<port>.sock")
 	s3Options.bindIp = cmdServer.Flag.String("s3.ip.bind", "", "ip address to bind to. If empty, default to same as -ip.bind option.")
 	s3Options.idleTimeout = cmdServer.Flag.Int("s3.idleTimeout", 10, "connection idle seconds")
+	s3Options.concurrentUploadLimitMB = cmdServer.Flag.Int("s3.concurrentUploadLimitMB", 128, "limit total concurrent upload size for S3")
+	s3Options.concurrentFileUploadLimit = cmdServer.Flag.Int("s3.concurrentFileUploadLimit", 0, "limit number of concurrent file uploads for S3, 0 means unlimited")
 
 	sftpOptions.port = cmdServer.Flag.Int("sftp.port", 2022, "SFTP server listen port")
 	sftpOptions.sshPrivateKey = cmdServer.Flag.String("sftp.sshPrivateKey", "", "path to the SSH private key file for host authentication")