feat(wren-ai-service): kubernetes session affinity for ai service

This PR introduces support for session affinity settings in the Kubernetes deployment of the AI service. As the AI service is stateful, scaling replicas can lead to increased errors for "query not found" if results are retrieved from the wrong pod. To address this, we are using Istio to manage session affinity and improve reliability.

How to validate?

Scale up the replicas of the service on the Kubernetes cluster:
```
kubectl scale deploy wren-ai-service-deployment --replicas=2
```

Create a test pod:

echo 'apiVersion: v1
kind: Pod
metadata:
  name: test-pod
  namespace: wren
spec:
  containers:
  - name: curl-container
    image: curlimages/curl:7.85.0
    command: ["/bin/sh", "-c", "while true; do sleep 3600; done"]  
  restartPolicy: Never
' | kubectl apply -f -

Access the test pod:

kubectl exec -it test-pod -n wren -- /bin/sh

Validate the health check endpoint with a header and trace the result in pod log:
```
curl -H 'user-session: sid-1' wren-ai-service-svc:5555/health
```

Canner / WrenAI

feat(wren-ai-service): kubernetes session affinity for ai service #613

How to validate?

See Also