feat: add GET /health endpoint for Docker/k8s liveness probes

crates/presentation/src/routes.rs

@@ -18,6 +18,7 @@ pub fn build_router(state: AppState, ap_router: Router) -> Router {
     let ap_router = ap_router.layer(GovernorLayer::new(ap_cfg));
 
     Router::new()
+        .route("/health", routing::get(health_handler))
         .merge(html_routes(rate_limit))
         .merge(api_routes(rate_limit))
         .nest_service("/static", ServeDir::new("static"))
@@ -26,6 +27,10 @@ pub fn build_router(state: AppState, ap_router: Router) -> Router {
         .merge(ap_router)
 }
 
+async fn health_handler() -> axum::Json<serde_json::Value> {
+    axum::Json(serde_json::json!({ "status": "ok" }))
+}
+
 fn per_minute(n: u64) -> Quota {
     let n = NonZeroU32::new(n.clamp(1, u32::MAX as u64) as u32).unwrap();
     Quota::requests_per_minute(n)