refactor(前端): shared / utils 不再 import oj 和 admin 下的任何东西

依赖方向原来是反的：顶栏、登录框、举手列表这些 shared 组件从 oj/ 里拿东西。
- 跨端的接口挪进 shared/api.ts（按 apps/web/CLAUDE.md 的分法）：学生端题目列表、
  出题人列表、这节课的题、待弹的成就
- 这节课的 store → shared/store/lesson.ts；头像 RankAvatar → shared/components
- 纯函数挪进 utils/：举手列表的错法归类 errorKind、它依赖的答案错误分类 wrongAnswer
  和 Python 报错翻译 pythonError、题目列表行的 toProblemRow
- 只有后台在用的出题人下拉 AuthorSelect 挪回 admin/components

纯搬家。首页、题目列表、题目页、排名、课堂看板、后台题目列表打开无报错，
顶栏题号框敲 1001 回车直达题目页。

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

apps/web/src/oj/rank/components/ChampionList.vue

@@ -3,7 +3,7 @@ import type { RankRow, WeeklyChampion } from "@oj2/contract"
 import { useThemeVars } from "naive-ui"
 import UserName from "shared/components/UserName.vue"
 import { parseTime } from "utils/functions"
-import RankAvatar from "./RankAvatar.vue"
+import RankAvatar from "shared/components/RankAvatar.vue"
 
 /** 本班最近几周的每周冠军，底下再挂这张榜上「进步最大」的那个人 */
 defineProps<{

apps/web/src/oj/rank/components/ClassDetailDrawer.vue

@@ -9,7 +9,7 @@ import { useBackClose } from "shared/composables/backClose"
 import { useBreakpoints } from "shared/composables/breakpoints"
 import { parseTime } from "utils/functions"
 import { useRankPalette } from "../palette"
-import RankAvatar from "./RankAvatar.vue"
+import RankAvatar from "shared/components/RankAvatar.vue"
 
 // Markdown 连着整套代码高亮（两百多 KB），这里要等点开 / AI 写完才用得上，别让它拖慢页面
 const Markdown = defineAsyncComponent(() => import("shared/components/Markdown.vue"))

apps/web/src/oj/rank/components/RankAvatar.vue

@@ -1,79 +0,0 @@
-<script setup lang="ts">
-import { useDark } from "@vueuse/core"
-import { rgba } from "shared/composables/tone"
-import { USERNAME_CLASS_RE } from "utils/constants"
-
-/**
- * 排名页的头像。九成以上的学生没换过头像（1797 个号是 default.png），一排一模一样的
- * 默认图分不出人，所以默认头像画成「名字最后一个字 + 彩色圆」，颜色按用户名固定 ——
- * 同一个人在领奖台、赛道、「你」那张卡里是同一个颜色。自己是实心绿。
- */
-const props = defineProps<{
-  username: string
-  avatar: string | null
-  size: number
-  me?: boolean
-}>()
-
-const isDark = useDark()
-/** 头像文件丢了（备份恢复后没拷上传目录、被删）就退回名字那个字，别露出破图 */
-const broken = ref(false)
-watch(
-  () => props.avatar,
-  () => (broken.value = false),
-)
-
-const PALETTE = ["#2f6fd0", "#c76a12", "#6a4bd8", "#0f7a6c", "#b4315f", "#4d5967", "#8a6a00"]
-
-const letter = computed(() => {
-  const name = props.username.replace(USERNAME_CLASS_RE, "") || props.username
-  return Array.from(name).at(-1) ?? "?"
-})
-
-const colors = computed(() => {
-  if (props.me) return { background: "#18a058", color: "#ffffff" }
-  let hash = 0
-  for (const char of props.username) hash = (hash * 31 + char.codePointAt(0)!) >>> 0
-  const base = PALETTE[hash % PALETTE.length]!
-  return { background: rgba(base, isDark.value ? 0.28 : 0.13), color: base }
-})
-</script>
-
-<template>
-  <img
-    v-if="avatar && !broken"
-    class="avatar"
-    :src="avatar"
-    alt=""
-    @error="broken = true"
-    :style="{ width: `${size}px`, height: `${size}px` }"
-  />
-  <span
-    v-else
-    class="avatar letter"
-    aria-hidden="true"
-    :style="{
-      width: `${size}px`,
-      height: `${size}px`,
-      fontSize: `${Math.round(size * 0.5)}px`,
-      ...colors,
-    }"
-    >{{ letter }}</span
-  >
-</template>
-
-<style scoped>
-.avatar {
-  border-radius: 50%;
-  flex-shrink: 0;
-  object-fit: cover;
-}
-
-.letter {
-  display: inline-flex;
-  align-items: center;
-  justify-content: center;
-  font-weight: 700;
-  line-height: 1;
-}
-</style>

apps/web/src/oj/rank/components/RankMe.vue

@@ -4,7 +4,7 @@ import { useThemeVars } from "naive-ui"
 import UserName from "shared/components/UserName.vue"
 import { gapText, toPass } from "../utils"
 import MoodPopover from "./MoodPopover.vue"
-import RankAvatar from "./RankAvatar.vue"
+import RankAvatar from "shared/components/RankAvatar.vue"
 
 export interface MiniRank {
   label: string

apps/web/src/oj/rank/components/RankPodium.vue

@@ -4,7 +4,7 @@ import { useThemeVars } from "naive-ui"
 import { useBreakpoints } from "shared/composables/breakpoints"
 import UserName from "shared/components/UserName.vue"
 import { useRankPalette } from "../palette"
-import RankAvatar from "./RankAvatar.vue"
+import RankAvatar from "shared/components/RankAvatar.vue"
 
 /**
  * 领奖台：前三名站在台阶上，第一名戴皇冠。赛道从第 4 名接着排，前三不再出现第二遍。

apps/web/src/oj/rank/components/RankTrack.vue

@@ -5,7 +5,7 @@ import UserName from "shared/components/UserName.vue"
 import { useBreakpoints } from "shared/composables/breakpoints"
 import { useRankPalette } from "../palette"
 import MoodPopover from "./MoodPopover.vue"
-import RankAvatar from "./RankAvatar.vue"
+import RankAvatar from "shared/components/RankAvatar.vue"
 
 /**
  * 赛道：每人一根条，条越长做对越多，一样长的先做到的排前面（设计稿 G1 / G2）。

apps/web/src/oj/rank/components/WeekTop.vue

@@ -3,7 +3,7 @@ import type { RankRow } from "@oj2/contract"
 import { useThemeVars } from "naive-ui"
 import UserName from "shared/components/UserName.vue"
 import { useRankPalette } from "../palette"
-import RankAvatar from "./RankAvatar.vue"
+import RankAvatar from "shared/components/RankAvatar.vue"
 
 /** 这周本班前 5 名（做对过新题的），每周一清零 */
 const props = defineProps<{ rows: RankRow[]; meId?: number; loaded: boolean }>()