Feature: add `h8 set port` command to add/remove ports on existing apps

[erfanium]

Description

Currently there is no way to modify the service ports of an existing app. To add or remove a port, you must delete the entire app and recreate it — which loses disk attachments, env vars, and other configuration.

Proposed Command

h8 set port APP PORTS...

Where PORTS is in the same svcPort:containerPort format as app create --port.

Examples:

h8 set port myapp 8080:8080           # set/replace all ports
h8 set port myapp 3000:3000           # remove SSH, keep only HTTP
h8 set port myapp 3000:3000 2222:22   # add SSH back

Workaround

Currently requires delete + recreate (destructive): h8 app delete then h8 app create with the desired ports, re-attach disk, re-set all env vars.