CHORE: Remove Tekton CI/CD platform

- Delete tekton/ directory (pipeline, triggers, dashboard, ci-cd)
- Remove tekton references from kustomization.yaml
- Switching to GitHub Actions for CI/CD

tekton/ci-cd/manifests/triggers/kustomization.yaml

@@ -1,10 +0,0 @@
-apiVersion: kustomize.config.k8s.io/v1beta1
-kind: Kustomization
-
-resources:
-  - rbac.yaml
-  - secret.yaml
-  - triggerbinding.yaml
-  - triggertemplate.yaml
-  - eventlistener.yaml
-  - ingress.yaml