Fix Open WebUI storage and model detection

- Change emptyDir to persistent volume (open-webui-data PVC)
  Fixes data loss on pod restart (admin user disappears)

- Add ENABLE_OLLAMA_API=false
  Disable broken Ollama endpoint probing
  vLLM uses OpenAI-compatible API, not Ollama

- Create pvc.yaml for persistent data storage
  10Gi NFS-backed storage via nfs-emporium StorageClass

cluster/applications/open-webui/deployment.yaml

@@ -59,6 +59,9 @@ spec:
           value: "true"
         - name: ENABLE_MODEL_FILTER
           value: "false"
+        # Disable Ollama model detection (we use vLLM/OpenAI-compatible only)
+        - name: ENABLE_OLLAMA_API
+          value: "false"
         # Storage
         - name: DATA_DIR
           value: "/app/backend/data"
@@ -82,5 +85,5 @@ spec:
           mountPath: /app/backend/data
       volumes:
       - name: data
-        emptyDir:
-          sizeLimit: 1Gi
+        persistentVolumeClaim:
+          claimName: open-webui-data