Add context menus and SFTP transfer progress handling

- Implemented context menu styles in components.css.
- Added SFTP transfer progress queue and related styles in sftp.css.
- Enhanced app.js to handle SFTP transfer progress events.
- Updated sftp.js to manage transfer progress and render the transfer queue.
- Modified terminal.js to include context menu shortcuts.
- Adjusted manager.go to emit SFTP transfer progress events with direction.
- Updated sshclient.go to modify terminal modes for better performance.

internal/sshclient/sshclient.go

@@ -159,8 +159,9 @@ func (c *Client) connectInternal(
 	rows := 24
 	modes := ssh.TerminalModes{
 		ssh.ECHO:          1,
-		ssh.TTY_OP_ISPEED: 14400,
-		ssh.TTY_OP_OSPEED: 14400,
+		ssh.TTY_OP_ISPEED: 115200,
+		ssh.TTY_OP_OSPEED: 115200,
+		ssh.IUTF8:         1,
 	}
 
 	if err := session.RequestPty(termType, rows, cols, modes); err != nil {