Add full GitLab application source support for git operations:
- Implement SSH-based authentication using private keys with configurable ports
- Support HTTP basic auth for HTTPS GitLab URLs (with or without deploy keys)
- Handle private key setup and SSH command configuration in both Docker and local modes
- Support merge request checkouts for GitLab with SSH authentication
Improvements to credential handling:
- URL-encode GitHub access tokens to handle special characters properly
- Update log sanitization to redact passwords from HTTPS/HTTP URLs
- Extend convertGitUrl() type hints to support GitlabApp sources
Add test coverage and seed data:
- New GitlabSourceCommandsTest with tests for private key and public repo scenarios
- Test for HTTPS basic auth password sanitization in logs
- Seed data for GitLab deploy key and public example applications
