Add support for Warpgate Userauth

[Lor4de]

Is your feature request related to a problem? Please describe.
Im using a selfhosted Warpgate instance and want to use the authentication from warpgate with webssh

Describe the solution you'd like
Maybe it should be enough to allow the following format for saved connections usernames:

-username-:-warpgate.connection.name-

The format for a warpgate ssh connection is:

ssh "-user-:-warpgate.connection.name-@ssh.warpgate.xxx" -p 22

Describe alternatives you've considered
I dont know any alternatives

Additional context

[bifrost0x]

@Lor4de will be implemented with the nex pr :)

[bifrost0x]

@Lor4de
Implemented in #238 containing:

1. As a WebSSH admin, enable Settings → Administration → Integrations → Warpgate / SSH gateway, then reload your workspace. It is disabled by default.
2. Create a connection with your Warpgate hostname and SSH port.
3. Use your-user:your-warpgate-target as the username, for example alice:production.
4. Choose password or SSH key authentication. For interactive login, select Password and leave it empty; follow the gateway's password, MFA or browser-approval prompts.

No additional Compose service or configuration is needed. Your Warpgate user must already have access to the target.

The short setup guide also covers target requirements and Quick SFTP limitations.

[Lor4de]

@bifrost0x
Hey, tested the new feature right now. Works perfectly - Thanks for the implementation 🥇