feat(web): add mobile-first read-only dashboard frontend

reaction_board/web/static/api.js

@@ -0,0 +1,56 @@
+export class ApiError extends Error {
+  constructor(message, status = 0, code = "error") {
+    super(message);
+    this.name = "ApiError";
+    this.status = status;
+    this.code = code;
+  }
+}
+
+function buildUrl(path, params) {
+  const url = new URL(path, window.location.origin);
+  if (params) {
+    for (const [key, value] of Object.entries(params)) {
+      if (value === null || value === undefined || value === "") continue;
+      url.searchParams.set(key, String(value));
+    }
+  }
+  return url;
+}
+
+export async function api(path, params) {
+  const response = await fetch(buildUrl(path, params), {
+    headers: { Accept: "application/json" },
+    credentials: "same-origin",
+  });
+  if (response.status === 401) {
+    window.location.href = "/login";
+    throw new ApiError("登录已失效，请重新登录", 401, "unauthorized");
+  }
+  let payload;
+  try {
+    payload = await response.json();
+  } catch {
+    throw new ApiError(`接口返回异常（HTTP ${response.status}）`, response.status);
+  }
+  if (!response.ok || !payload.ok) {
+    const error = payload.error || {};
+    throw new ApiError(
+      error.message || `请求失败（HTTP ${response.status}）`,
+      response.status,
+      error.code || "error",
+    );
+  }
+  return payload.data;
+}
+
+export function apiUrl(path, params) {
+  return buildUrl(path, params).toString();
+}
+
+export async function health() {
+  const response = await fetch("/api/health", { 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;
+}