feat(web): require login only for candidates and system

reaction_board/web/static/api.js

@@ -50,3 +50,10 @@ export async function health() {
   const payload = await response.json();
   return payload?.data ?? payload;
 }
+
+export async function session() {
+  const response = await fetch("/api/session", { credentials: "same-origin" });
+  if (!response.ok) throw new ApiError("无法连接看板服务", response.status);
+  const payload = await response.json();
+  return payload?.data ?? payload;
+}