Improve kustomization usage

Ensure that the `manifest/base` folder can be used as a standalone
kustomization resource.

Add a new subfolder `manifest/gpu` which uses `manifest/base` with
additional GPU related patches.

kubernetes/manifest/gpu/kustomization.yaml

@@ -0,0 +1,8 @@
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+
+resources:
+  - ../base
+
+patches:
+- path: ollama-statefulset-gpu.yaml