[FEATURE] Support gitlab in ultraplan

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

I want to use ultraplan because this is a great idea. Reviewing and updating plans on a text interface is not convenient.
But my repos are on gitlab, I cannot move them and should not have to.

Can you support Gitlab as well as Github?

Proposed Solution

Add Gitlab support to Claude Code to match Github.

Alternative Solutions

_No response_

Priority

Critical - Blocking my work

Feature Category

CLI commands and flags

Use Case Example

_No response_

Additional Context

_No response_