feat: refactor observability configs for Compose and add for Local

[JaredforReal]

What type of PR is this?
feat: refactor observability configs for Compose and add for Local

What this PR does / why we need it:

• Use Docker to set up Grafana and Prometheus for Local Installation, which is mostly the same as Docker Compose Deployment, so this PR merges them together like:

tools/observability/   # unified for local and compose
├── prometheus.yaml              
├── grafana-datasource.yaml
├── grafana-dashboard.yaml
├── llm-router-dashboard.json
├── README.md
└── scripts/
    ├── start-observability.sh
    └── stop-observability.sh

docker-compose.obs.yml           # Local
docker-compose.yml               # Compose（updated to use configs in tools/observability/）

• Original configs for Grafana and Prometheus in config/ are no longer needed.
• Update docs/tutorials/observability/observability.md.
• Introduce new make commands for easy access.

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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:

📁 Root Directory

Owners: @rootfs, @Xunzhuo
Files changed:

• docker-compose.obs.yml
• Makefile
• docker-compose.yml

📁 tools

Owners: @yuluo-yx, @rootfs, @Xunzhuo
Files changed:

• tools/make/observability.mk
• tools/observability/README.md
• tools/observability/grafana-dashboard.yaml
• tools/observability/grafana-datasource.yaml
• tools/observability/llm-router-dashboard.json
• tools/observability/prometheus.yaml
• tools/observability/scripts/start-observability.sh
• tools/observability/scripts/stop-observability.sh
• tools/make/common.mk

📁 website

Owners: @Xunzhuo
Files changed:

• website/docs/tutorials/observability/observability.md

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🎉 Thanks for your contributions!

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

[JaredforReal]

Need further test, leave it as a draft.