fix(ui): 评估列表默认分页改为 20，符合 ADR-0005

- 将 pageSize 默认值从 10 改为 20
- 遵循 ADR-0005 "超过 20 行才分页（pageSize 20）" 规范

frontend/web/src/pages/IntelligentEvals.tsx

@@ -61,7 +61,7 @@ export default function IntelligentEvalsPage() {
   const [createOpen, setCreateOpen] = useState(false)
   const [statusFilter, setStatusFilter] = useState('all')
   const [page, setPage] = useState(1)
-  const [pageSize, setPageSize] = useState(10)
+  const [pageSize, setPageSize] = useState(20)
   const [submitting, setSubmitting] = useState(false)
   const [form] = Form.useForm<CreateFormValues>()