fix: 电商视频生成链路稳定性 — AI超时/重试/断点续传 + 404页面 + DashScope Key移除

- adVideoPlanClient: 模型级联降级(qwen-max→plus→turbo), 5xx/网络错误可重试, 超时延长至180s, 错误信息包含上游响应体
- 服务端ai/chat: 超时60s→120s, AbortError返回504(非500), PM2已热重载
- EcommerceVideoWorkspace: 策划失败后支持从断点继续(保留已完成步骤的中间产物), 分镜图/视频生成仅重做失败场景
- scriptEvalClient: 移除客户端DASHSCOPE_API_KEY引用(Nginx代理注入)
- NotFoundPage: 未知路由显示404页面(替代兜底跳首页)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/components/NotFoundPage.tsx

@@ -0,0 +1,24 @@
+import { HomeOutlined } from "@ant-design/icons";
+import { useCallback } from "react";
+
+interface NotFoundPageProps {
+  onGoHome: () => void;
+}
+
+function NotFoundPage({ onGoHome }: NotFoundPageProps) {
+  return (
+    <section className="not-found-page page-motion">
+      <div className="not-found-page__content">
+        <div className="not-found-page__code">404</div>
+        <h1>页面未找到</h1>
+        <p>您访问的页面不存在或已被移除。</p>
+        <button type="button" className="not-found-page__button" onClick={onGoHome}>
+          <HomeOutlined />
+          返回首页
+        </button>
+      </div>
+    </section>
+  );
+}
+
+export default NotFoundPage;