refactor: establish standalone application boundary

app/frontend/bootstrap.js

@@ -0,0 +1,39 @@
+const PAGE_REGISTRY_URL = "/pages.config.js?v=20260803-2";
+
+function loadRuntimeScripts(sources) {
+  return Promise.all(sources.map((src) => new Promise((resolve, reject) => {
+    const script = document.createElement("script");
+    script.src = src;
+    script.async = false;
+    script.addEventListener("load", resolve, { once: true });
+    script.addEventListener("error", () => reject(new Error(`无法加载运行脚本：${src}`)), { once: true });
+    document.body.append(script);
+  })));
+}
+
+async function loadPageFragment(fragment) {
+  const response = await fetch(fragment.url, { credentials: "same-origin" });
+  if (!response.ok) {
+    throw new Error(`无法加载页面片段：${fragment.url}（HTTP ${response.status}）`);
+  }
+  return response.text();
+}
+
+async function bootstrap() {
+  await import(PAGE_REGISTRY_URL);
+  const registry = window.XiaobaiPages;
+  const mount = document.querySelector(".app-main");
+  if (!registry || !mount) throw new Error("页面注册表或挂载点不存在");
+
+  const fragments = await Promise.all(registry.fragments.map(loadPageFragment));
+  fragments.forEach((markup) => mount.insertAdjacentHTML("beforeend", markup));
+  await loadRuntimeScripts(registry.runtimeScripts);
+  document.body.dataset.runtimeReady = "true";
+}
+
+bootstrap().catch((error) => {
+  document.body.dataset.bootstrapError = "true";
+  const status = document.querySelector("#statusText");
+  if (status) status.textContent = error?.message || "页面初始化失败";
+  setTimeout(() => { throw error; });
+});