Add .gitlab-ci.yml with multi-platform build matrix (linux-x86_64,
linux-arm64, macos-arm64) and GitLab Release publish pipeline.
Rewrite scripts/install.sh to use GitLab API instead of GitHub API.
Replace all github.com/AgenticEconomics/webuild references with
git.jarvikheart.cn/jerryzhang/webuild across source, docs, and scripts.