feat: add dashboard & openwebui to k8s deploy

[JaredforReal]

What this PR does / why we need it:

• delete dashboard/deploy/
• add dashboard/, openwebui/, pipelines/ to deploy/kubernetes/observability/
• update deploy/docker-compose/README.md
• update deploy/kubernetes/README.md
• update deploy/kubernetes/observability/README.md

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[github-actions]

👥 vLLM Semantic Team Notification

The following members have been identified for the changed files in this PR and have been automatically assigned:

📁 deploy

Owners: @rootfs, @Xunzhuo
Files changed:

• deploy/kubernetes/observability/dashboard/configmap.yaml
• deploy/kubernetes/observability/dashboard/deployment.yaml
• deploy/kubernetes/observability/dashboard/service.yaml
• deploy/kubernetes/observability/openwebui/deployment.yaml
• deploy/kubernetes/observability/pipelines/deployment.yaml
• deploy/kubernetes/observability/pipelines/vllm_semantic_router_pipe.py
• deploy/docker-compose/README.md
• deploy/kubernetes/README.md
• deploy/kubernetes/observability/README.md
• deploy/kubernetes/observability/ingress.yaml
• deploy/kubernetes/observability/kustomization.yaml

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🎉 Thanks for your contributions!

This comment was automatically generated based on the OWNER files in the repository.

[JaredforReal]

need more test, leave it as draft