feat(core): SSH port forwarding and tunnel assistant (local, remote, and SOCKS5)

[WhiteRoseLK]

Is your feature request related to a problem?

Developers frequently use SSH to forward ports (e.g., accessing a remote database, forwarding a local web server, or launching a dynamic SOCKS5 proxy). Configuring and remembering -L, -R, and -D options can be cumbersome.

Describe the solution you'd like

1. Add an interactive Port Forwarding modal in the TUI (e.g., pressing Shift+T or L):
   • Local forwarding (-L local_port:target_host:target_port)
   • Remote forwarding (-R remote_port:target_host:target_port)
   • Dynamic SOCKS5 proxy (-D local_port)
2. Allow saving favorite tunnel profiles per host in ~/.neossh/settings.json.
3. Provide a command copy shortcut to easily copy the generated ssh -L ... command line to the clipboard.

Describe alternatives you've considered

Typing long manual commands like ssh -L 5432:localhost:5432 user@host from scratch each time.