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/kustomization.yaml

@@ -1,16 +0,0 @@
-apiVersion: kustomize.config.k8s.io/v1beta1
-kind: Kustomization
-
-resources:
-  # Secrets
-  - secrets/zot-registry-secret.yaml
-  - secrets/github-credentials.yaml
-  # Tasks
-  - tasks/git-clone.yaml
-  - tasks/buildah-build-push.yaml
-  # Pipelines
-  - pipelines/nextjs-pipeline.yaml
-  - pipelines/fastapi-pipeline.yaml
-  - pipelines/python-pipeline.yaml
-  # Triggers
-  - triggers/