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/dashboard/manifests/ingress.yaml

@@ -1,25 +0,0 @@
-apiVersion: networking.k8s.io/v1
-kind: Ingress
-metadata:
-  name: tekton-dashboard
-  namespace: tekton-pipelines
-  annotations:
-    cert-manager.io/cluster-issuer: letsencrypt-prod
-    traefik.ingress.kubernetes.io/router.middlewares: authelia-authelia-auth@kubernetescrd
-spec:
-  ingressClassName: traefik
-  tls:
-  - hosts:
-    - tekton0213.kro.kr
-    secretName: tekton-dashboard-tls
-  rules:
-  - host: tekton0213.kro.kr
-    http:
-      paths:
-      - path: /
-        pathType: Prefix
-        backend:
-          service:
-            name: tekton-dashboard
-            port:
-              number: 9097