feat: use external hostname with IP address fallback for SSH URI

[runleveldev]

This pull request updates how SSH and HTTP host information is handled and displayed for containers, ensuring that the correct external host is used for SSH connections in both the backend and frontend. The changes improve reliability when generating SSH and HTTP URLs, especially in environments where an external domain is configured.

Backend improvements to host information:

• Refactored the construction of the HTTP external host and URL in containers.js to separate the host from the full URL, enabling reuse of the host for SSH connections. (create-a-container/routers/containers.js, create-a-container/routers/containers.jsL181-R184)
• Added a new sshHost field to the container object, preferring the HTTP external host if available, otherwise falling back to the site's external IP. (create-a-container/routers/containers.js, create-a-container/routers/containers.jsR198)

Frontend updates for SSH links:

• Updated the SSH connection links in the containers index view to use the new sshHost value instead of always using the site's external IP, ensuring links point to the correct external hostname when available. (create-a-container/views/containers/index.ejs, create-a-container/views/containers/index.ejsL76-R79)