refactor: #be rename k8s folder

backend/k8s/base/database/deployment.yaml

backend/k8s/base/database/kustomization.yaml

backend/k8s/base/database/pvc.yaml

backend/k8s/base/database/service.yaml

backend/k8s/base/kustomization.yaml

backend/k8s/base/webserver/deployment.yaml

backend/k8s/base/webserver/ingress.yaml

backend/k8s/base/webserver/kustomization.yaml

backend/k8s/base/webserver/service.yaml

backend/k8s/overlays/dev/database.deployment.yaml

backend/k8s/overlays/dev/kustomization.yaml

backend/k8s/overlays/dev/webserver.deployment.yaml

backend/k8s/overlays/dev/webserver.ingress.patch.yaml

backend/k8s/overlays/stg/database.deployment.yaml

backend/k8s/overlays/stg/kustomization.yaml

backend/k8s/overlays/stg/webserver.deployment.yaml

backend/k8s/overlays/stg/webserver.ingress.patch.yaml