Add support for integrating with external Git hosts (GitLab, Gitea,
and Azure DevOps). The backend gains a client to fetch paginated
repository lists, normalise base URLs, and surface provider errors.
Credentials are loaded from the OS keychain and a Tauri command is
exposed for the frontend to list integration repositories.
- Implement integration client with pagination, deserialization,
and provider-specific handling.
- Centralise keychain credential loading and expose listing command.
- Update UI to manage integration metadata, persist settings, and
save/remove tokens to the OS keychain for cloning and operations.
Christoph
91263547db