Initial release of the Dagger GitLab CI component.

This component provides a reusable GitLab CI/CD component for executing
`dagger call` in pipelines with a single interface supporting both:

- Docker executor (Docker-in-Docker)
- Kubernetes executor (pre-provisioned Dagger Engine)

Features:
- Typed GitLab component inputs (`spec:inputs`)
- Executor selection via `executor: docker | kubernetes`
- Pinned Dagger CLI installation
- Optional debug mode (`--debug --progress=plain`)
- Support for DAGGER_CLOUD_TOKEN
- Customizable job name, stage, rules, needs, and runner tags

Repository structure follows GitLab CI Component best practices.

Example usage:

include:
  - component: $CI_SERVER_FQDN/<group>/<project>/call@v1.0.0
    inputs:
      function: test