feat: 改版阶段 1：统一顶栏和教学侧栏、配色和图标规范、路由角色守卫

- 所有页面共用顶栏（教程 / 挑战 / 自由创作 / 作品展，右边“教学”和用户菜单）；
  没登录时顶栏有“登录”按钮，关掉登录框不再白屏；/submission/:id 全屏页不带顶栏
- 后台改成“教学”侧栏，分出题 / 班级 / 管理三组；“全部提交”留在侧栏里打开；
  admin 也能进作品展管理（后端本来就允许）
- 路由按角色守卫：meta.role 为 staff / super，学生和 admin 进不了无权页面
- 配色只在 theme.ts 定义，同时生成 --wp-* CSS 变量和 Naive UI 主题，暗色值先定好
- 图标改用打包进来的 lucide（断网也能显示），去掉 @iconify/vue 和 PUBLIC_ICONIFY_URL；
  代码字体换成打包的 JetBrains Mono，编辑器默认字号 24 → 16
- 教程面板去掉和顶栏重复的切换和图标按钮，图标按钮都补上文字或提示

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

CLAUDE.md

@@ -26,7 +26,10 @@ The backend was rewritten from Django in 2026-10 to cut memory use (~25 MB vs. 1
   - UI framework: **Naive UI** (auto-imported via `unplugin-vue-components`)
   - `src/token.ts` — tokens in localStorage; refreshes the access token shortly before expiry (one request at a time) and builds WebSocket URLs
   - `src/api.ts` — Axios-based API client; adds the Bearer header, on 401 refreshes once and retries, otherwise clears login and goes home; 403 alerts and goes home
-  - `src/router.ts` — Vue Router with auth guards
+  - `src/router.ts` — Vue Router; `meta.auth` needs login, `meta.role` (`staff` = admin+super, `super`) is checked in the guard after `store/session.loadUser()`, `meta.bare` pages render without the top bar
+  - `src/theme.ts` — the only place colors are defined: one palette (light + dark values) becomes both `--wp-*` CSS variables and Naive UI `themeOverrides`; use `var(--wp-...)` in styles, never hard-coded colors. No `color-mix()` (Chrome 105)
+  - `src/icons.ts` — `<Icon icon="lucide:name" />` renders bundled `lucide-vue-next` icons (works offline); register new names in its map. Fonts are bundled too (`@fontsource/jetbrains-mono`)
+  - `components/layout/AppShell.vue` — top bar for every page; `pages/Dashboard.vue` is the teaching sidebar (“教学”) under `/dashboard`
   - `src/store/` — Reactive state (plain Vue refs, not Vuex/Pinia); `prompt.ts` / `guidance.ts` own the WebSockets
   - `src/pages/`, `src/components/` — user management uses `components/dashboard/UserFormModal.vue` (there is no Django Admin anymore)