chore: migrate CRD API group from reaper.io to reaper.giar.dev

[miguelgila]

Problem

The CRD API group is currently reaper.io across the entire codebase, but should be reaper.giar.dev to match the project's actual domain.

Scope

This is a breaking change for any existing CRD installations — all ReaperPod resources would need to be recreated after the migration.

Files affected

Grep for reaper\.io shows occurrences in:

• CRD definition: src/crds/reaper_pod.rs (kube derive macro group = "reaper.io")
• Controller: src/bin/reaper-controller/pod_builder.rs (owner label reaper.io/owner, apiVersion)
• Generated CRDs: deploy/helm/reaper/crds/, deploy/kubernetes/crds/
• Helm templates: deploy/helm/reaper/templates/controller-rbac.yaml
• Static manifests: deploy/kubernetes/reaper-controller.yaml
• Documentation: README.md, CLAUDE.md, docs/CRD_PLAN.md, docs/book/
• Examples: examples/09-reaperpod/
• Scripts: scripts/generate-crds.sh, scripts/setup-playground.sh, scripts/lib/test-integration-suite.sh

Suggested approach

1. Update the group in src/crds/reaper_pod.rs and owner label/apiVersion in pod_builder.rs
2. Regenerate CRDs via scripts/generate-crds.sh
3. Update all RBAC, manifests, docs, examples, and test scripts
4. Document the migration path for existing users (delete old CRD, install new one)
5. Consider doing this alongside a version bump (v1alpha1 → v1alpha1 with new group)