fix: cache github token and handle expiry for gitgo new

[Huerte]

Type

• Bug fix
• New feature
• Documentation
• Refactor / internal

Overview

the new command was opening the browser to ask for a token every single time. this fixes that by saving the token locally after the first time you paste it. it also catches expired tokens so you dont get stuck with a failing command.

Changes

• gitgo new: saves the token to gitgo.github-token in your git config so it reuses it next time
• gitgo new: catches 401 errors from github, deletes the dead token, and automatically asks for a new one
• gitgo new: opens the classic token page by default so you can select the no expiration option
• utils/config.py: adds a silent flag to set_config so the raw token doesnt leak into the terminal output

How to Test

1. pip install -e ".[dev]"
2. run gitgo new test-repo1 and paste your token when it asks
3. run gitgo new test-repo2
4. Expected result: the second run creates the repo immediately without opening the browser or asking for the token again

Checklist

• I tested my changes locally and they work
• I updated CHANGELOG.md under the [Unreleased] section
• I updated README.md (if I added or changed a command)
• I added or updated tests for my change (if applicable)
• My change does not break any existing commands (if it does, describe the impact in the Overview)