feat: add runnable simulator foundation

app/observability/__init__.py

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+"""Health, metrics, and tracing adapters."""

app/observability/health.py

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+"""Kubernetes-compatible health endpoints."""
+
+from __future__ import annotations
+
+from typing import Annotated
+
+from fastapi import APIRouter, Depends, Response, status
+from pydantic import BaseModel
+
+from app.db.pool import Database
+from app.dependencies import get_database
+
+router = APIRouter(prefix="/health", tags=["health"])
+
+
+class HealthResponse(BaseModel):
+    status: str
+
+
+@router.get("/live", response_model=HealthResponse)
+async def live() -> HealthResponse:
+    """Report process liveness without checking dependencies."""
+
+    return HealthResponse(status="ok")
+
+
+@router.get("/ready", response_model=HealthResponse)
+async def ready(
+    response: Response,
+    database: Annotated[Database, Depends(get_database)],
+) -> HealthResponse:
+    """Report whether the required database dependency is usable."""
+
+    if await database.is_ready():
+        return HealthResponse(status="ok")
+    response.status_code = status.HTTP_503_SERVICE_UNAVAILABLE
+    return HealthResponse(status="unavailable")