feat(web): CopilotAlert 告警组件 + 告警 API 扩展

- CopilotAlert: 分级告警列表，30秒轮询刷新，危急 banner
- copilot.ts 新增 listAlerts 函数

apps/web/src/api/copilot.ts

@@ -54,6 +54,10 @@ export function dismissInsight(id: string) {
   return client.post(`/copilot/insights/${id}/dismiss`);
 }
 
+export function listAlerts(params?: { severity?: string; page?: number; page_size?: number }) {
+  return listInsights({ insight_type: 'anomaly', ...params });
+}
+
 export function listRules(params?: { page?: number; page_size?: number }) {
   return client.get<PaginatedResponse<Record<string, unknown>>>('/copilot/rules', { params });
 }