feat: /health エンドポイントを正式実装する

src/example/app.py

@@ -4,6 +4,7 @@
 from fastapi.responses import JSONResponse
 
 from nene2.config import AppSettings
+from nene2.http import HealthStatus
 from nene2.middleware import ErrorHandlerMiddleware
 from nene2.validation.exceptions import ValidationException
 
@@ -73,9 +74,11 @@ def create_app(settings: AppSettings | None = None) -> FastAPI:
         )
     )
 
-    @app.get("/health")
+    @app.get("/health", tags=["system"], summary="Health check")
     async def health() -> JSONResponse:
-        return JSONResponse({"status": "ok"})
+        status = HealthStatus(status="ok")
+        code = 200 if status.is_healthy else 503
+        return JSONResponse({"status": status.status, "checks": status.checks}, status_code=code)
 
     return app
 

src/nene2/http/__init__.py

@@ -1,9 +1,12 @@
-"""HTTP helpers — JSON responses, pagination, problem details."""
+"""HTTP helpers — JSON responses, pagination, problem details, health."""
 
+from .health import HealthCheckProtocol, HealthStatus
 from .pagination import PaginationQuery, PaginationQueryParser, PaginationResponse
 from .problem_details import problem_details_response
 
 __all__ = [
+    "HealthCheckProtocol",
+    "HealthStatus",
     "PaginationQuery",
     "PaginationQueryParser",
     "PaginationResponse",

src/nene2/http/health.py

@@ -0,0 +1,20 @@
+"""HealthCheckProtocol and HealthStatus — framework health check contract."""
+
+from dataclasses import dataclass, field
+from typing import Protocol
+
+
+@dataclass(frozen=True, slots=True)
+class HealthStatus:
+    status: str
+    checks: dict[str, str] = field(default_factory=dict)
+
+    @property
+    def is_healthy(self) -> bool:
+        return self.status == "ok"
+
+
+class HealthCheckProtocol(Protocol):
+    """Contract for application health checks."""
+
+    def check(self) -> HealthStatus: ...