perf: 首屏 JS 减少 2/3、随机评分查询提速，WebSocket 防刷和登录限流

- prettier 点“整理”时才加载，编辑器页面按路由懒加载：首屏 JS 2345 KB → 766 KB
- 随机评分先随机抽 64 个 rowid 挑选，抽不中再退回全表随机：6 万条提交时 50ms → 1ms
- WebSocket 消息最大 64 KB；AI 回复中再发来的消息直接拒绝，不再排队
- 同一用户名 10 分钟失败 10 次、同一 IP 失败 100 次后暂停登录（返回 429，登录框显示提示）
- 作品展的 iframe 加 loading="lazy"
- 新增 ws.test.ts（正常生成、回复中再发消息、中途断开、握手失败）和随机评分、登录限流的测试

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

client/src/components/editor/Editors.vue

@@ -79,11 +79,6 @@
 </template>
 <script lang="ts" setup>
 import { Icon } from "@iconify/vue"
-import prettier from "prettier/standalone"
-import * as htmlParser from "prettier/parser-html"
-import * as cssParser from "prettier/parser-postcss"
-import * as babelParser from "prettier/parser-babel"
-import * as estreeParser from "prettier/plugins/estree"
 import Editor from "./Editor.vue"
 import Toolbar from "./Toolbar.vue"
 import { html, css, js, tab, size, reset } from "../../store/editors"
@@ -105,6 +100,15 @@ function changeSize(num: number) {
 }
 
 async function formatCode() {
+  // prettier 加上各语言插件近 1MB，只在点“格式化”时才加载
+  const [prettier, htmlParser, cssParser, babelParser, estreeParser] =
+    await Promise.all([
+      import("prettier/standalone"),
+      import("prettier/parser-html"),
+      import("prettier/parser-postcss"),
+      import("prettier/parser-babel"),
+      import("prettier/plugins/estree"),
+    ])
   const [htmlFormatted, cssFormatted, jsFormatted] = await Promise.all([
     prettier.format(html.value, {
       parser: "html",