feat(backend): add swagger-ui endpoint via utoipa

backend/src/web/routes_health.rs

@@ -1,9 +1,21 @@
 use axum::{Router, routing::get};
+use utoipa::OpenApi;
+
+#[derive(OpenApi)]
+#[openapi(paths(health))]
+pub struct HealthApi;
 
 pub fn routes_health() -> Router {
     Router::new().route("/health", get(health))
 }
 
+/// Health check
+#[utoipa::path(
+    get,
+    path = "/health",
+    tag = "health",
+    responses((status = 200, description = "Service is healthy"))
+)]
 async fn health() -> &'static str {
     "up"
 }