Root cause of CI failure: Pipeline 'poimen-ci' didn't exist in cluster.
PipelineRuns failed with CouldntGetPipeline, CI gate blocked :latest promotion.
- Added tekton-pipeline.yaml with Pipeline + Task to k8s/app/
- Added to kustomization.yaml so ArgoCD reconciles it
- Task runs curl smoke tests (health, ingest, query) against live service
instead of broken cargo test inside runtime image
