fix(ux): surface hidden notices, bound report waits, add root boundaries

Framework-level UX fixes found while auditing staging (BUG-216..220).

- chat: route 44 previously discarded composer notices to sonner with
  dedupe, so recovery, cancel and archive feedback is actually visible
  (BUG-216)
- chat: anchor stream auto-scroll to bottom proximity and add a
  jump-to-latest control, so reading history is no longer interrupted
  on every token (BUG-218)
- reports: replace the silent 120s poll cutoff with an explicit
  timed-out state, an 8m budget, stepped backoff and an elapsed
  counter (BUG-217)
- reports: pause polling while the tab is hidden, via a shared hook
- app: add root error, global-error and not-found boundaries (BUG-219)
- admin: add antd SSR style extraction and the React 19 render adapter,
  and move admin-only css out of the global stylesheet (BUG-220)
- membership: run bootstrap fetches concurrently and pause payment
  polling while hidden
- build: configure optimizePackageImports

Verified on top of 2d370f2e: tsc, eslint, next build, and the related
frontend contract suites.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/lib/chat-notice.ts

@@ -0,0 +1,39 @@
+import { toast } from "sonner";
+
+export const chatNoticeToastId = "chat-notice";
+
+export type NoticeTone = "info" | "success" | "error";
+
+const ongoingNotice = /正在|请稍候|请先|联网后/;
+const failedNotice = /失败|无法|不可用|未找到/;
+const settledNotice = /^已|^回答已恢复/;
+
+export function noticeTone(message: string): NoticeTone {
+  if (ongoingNotice.test(message)) return "info";
+  if (failedNotice.test(message)) return "error";
+  if (settledNotice.test(message)) return "success";
+  return "info";
+}
+
+let lastNotice = "";
+
+export function showChatNotice(message: string) {
+  if (!message.trim()) {
+    if (!lastNotice) return;
+    lastNotice = "";
+    toast.dismiss(chatNoticeToastId);
+    return;
+  }
+  if (lastNotice === message) return;
+  lastNotice = message;
+  const tone = noticeTone(message);
+  if (tone === "success") {
+    toast.success(message, { id: chatNoticeToastId });
+    return;
+  }
+  if (tone === "error") {
+    toast.error(message, { id: chatNoticeToastId });
+    return;
+  }
+  toast(message, { id: chatNoticeToastId });
+}