Add Pydantic models and FastAPI router structure for agent and backend

backend/app/routers/health.py

@@ -0,0 +1,35 @@
+import time
+from datetime import datetime, timezone
+
+from fastapi import APIRouter
+
+from app.schemas import HealthCheck, HealthResponse
+
+router = APIRouter(tags=['health'])
+START_TIME = time.time()
+
+
+def build_health() -> HealthResponse:
+    return HealthResponse(
+        status='pass',
+        service='netmapper-backend',
+        version='0.1.0',
+        time=datetime.now(timezone.utc),
+        uptime_s=round(time.time() - START_TIME, 2),
+        checks={'db': HealthCheck(status='warn', detail='database not configured yet')},
+    )
+
+
+@router.get('/live', response_model=HealthResponse)
+def live() -> HealthResponse:
+    return build_health()
+
+
+@router.get('/ready', response_model=HealthResponse)
+def ready() -> HealthResponse:
+    return build_health()
+
+
+@router.get('/health', response_model=HealthResponse)
+def health() -> HealthResponse:
+    return build_health()