feat: a unified Grafana + Prometheus entry for Local, Docker Compose, and k8s.

[JaredforReal]

Is your feature request related to a problem? Please describe.
Problem:

1. We don't have Observability (Grafana+Prom) for Local installation.
2. Configs for Docker Compose are highly sparse: config/prometheus.yaml, config/grafana/, deploy/llm-router-dashboard.json, docker-compose.yml.
3. Complicated and high-barrier setting up procedure.

What we have:
We have a unified architecture: same port 9190 from Prometheus, same dashboard json from deploy/llm-router-dashboard.json

Describe the solution you'd like

1. Pack Docker Compose related files to deploy/docker/, and create a make file in /tools/make for a unified and quick start, just like chore: move all dockerfile into tools #274 .
2. Refactor Observability files:

semantic-router/
├── config/
│   ├── observability/
│   │   ├── base/                      # basic config template
│   │   │   ├── prometheus.yaml
│   │   │   └── grafana-datasource.yaml
│   │   ├── local/                     # Local overlay
│   │   ├── docker/                    # Docker overlay
│   │   └── kubernetes/                # K8s overlay
│   ├── llm-router-dashboard.json      # unified grafana dashboard layout
│   └── config.yaml                    # Router configs ...
│
├── deploy/
│   ├── docker/
│   └── kubernetes/
│       └── observability/   # k8s advanced manifests and config: PVC...
│
├── scripts/  # optional
│   ├── generate-observability-config.sh 
│   └── start-observability.sh        
│
└── Makefile # optional
    ├── run-observability-local
    ├── run-observability-docker
    └── run-observability-k8s

Additional context
A preparation for #325

[JaredforReal]

changed mind after practicing. see new PR