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/triggers/kustomization.yaml

@@ -1,16 +0,0 @@
-apiVersion: kustomize.config.k8s.io/v1beta1
-kind: Kustomization
-
-resources:
-- https://storage.googleapis.com/tekton-releases/triggers/latest/release.yaml
-- https://storage.googleapis.com/tekton-releases/triggers/latest/interceptors.yaml
-
-patches:
-- target:
-    group: apiextensions.k8s.io
-    version: v1
-    kind: CustomResourceDefinition
-  patch: |-
-    - op: replace
-      path: /metadata/labels/app.kubernetes.io~1instance
-      value: tekton-triggers