feat(achievement): 添加奖杯馆页面

三种视觉状态：已解锁显示日期与获得率；未解锁公开成就显示进度条；
未解锁隐藏成就只显示稀有度，不画进度条（会泄露后端刻意遮掉的门槛）。
lte 类成就（如最短代码 ≤ 50 字符）不画百分比条，改为显示当前最好成绩。

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/oj/achievement/components/AchievementCard.vue

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+<script setup lang="ts">
+import type { Achievement } from "utils/types"
+
+const props = defineProps<{ achievement: Achievement }>()
+
+const RARITY_COLOR: Record<string, string> = {
+  bronze: "#b87333",
+  silver: "#9fa6b2",
+  gold: "#e0a300",
+  platinum: "#7dd3fc",
+}
+
+const RARITY_LABEL: Record<string, string> = {
+  bronze: "青铜",
+  silver: "白银",
+  gold: "黄金",
+  platinum: "白金",
+}
+
+// 隐藏且未解锁：后端已把名称/描述/图标和条件三件套都遮成 ??? 和 null，
+// 这里只负责不要把 null 渲染出来，也不要画出会泄露门槛的进度条
+const masked = computed(
+  () => props.achievement.hidden && !props.achievement.unlocked,
+)
+
+// 获得率低于 5% 的加稀有闪光边框
+const isRare = computed(
+  () => props.achievement.unlock_rate > 0 && props.achievement.unlock_rate < 5,
+)
+
+// 只有"越多越好"的成就画进度条。lte 类（如最短 AC 代码 ≤ 50 字符）
+// 画成百分比毫无意义，改成直接显示当前最好成绩
+const showProgressBar = computed(
+  () =>
+    !masked.value &&
+    !props.achievement.unlocked &&
+    props.achievement.operator === "gte" &&
+    props.achievement.threshold !== null,
+)
+
+const showBestSoFar = computed(
+  () =>
+    !masked.value &&
+    !props.achievement.unlocked &&
+    props.achievement.operator === "lte" &&
+    props.achievement.threshold !== null,
+)
+
+const percent = computed(() => {
+  const { progress, threshold } = props.achievement
+  if (threshold === null || threshold <= 0) return 100
+  return Math.min(100, Math.round(((progress ?? 0) / threshold) * 100))
+})
+
+const unlockDate = computed(() => {
+  const { unlock_time, backfilled } = props.achievement
+  // 补发的记录不显示具体日期：一次补发会给几百人盖上同一个时间戳
+  if (backfilled || !unlock_time) return "已获得"
+  return `${new Date(unlock_time).toLocaleDateString()} 获得`
+})
+</script>
+
+<template>
+  <n-card
+    size="small"
+    :class="{ locked: !achievement.unlocked, rare: isRare }"
+    :style="{ borderColor: RARITY_COLOR[achievement.rarity] }"
+  >
+    <div class="row">
+      <div class="icon">{{ achievement.icon }}</div>
+      <div class="body">
+        <div class="title">
+          <span class="name">{{ achievement.name }}</span>
+          <n-tag
+            size="tiny"
+            :color="{
+              borderColor: RARITY_COLOR[achievement.rarity],
+              textColor: RARITY_COLOR[achievement.rarity],
+            }"
+          >
+            {{ RARITY_LABEL[achievement.rarity] }}
+          </n-tag>
+        </div>
+        <div class="desc">{{ achievement.description }}</div>
+
+        <div v-if="achievement.unlocked" class="meta">
+          <span>{{ unlockDate }}</span>
+          <span class="rate">仅 {{ achievement.unlock_rate }}% 的人获得</span>
+        </div>
+
+        <div v-else-if="showProgressBar" class="meta">
+          <n-progress
+            type="line"
+            :percentage="percent"
+            :height="6"
+            :show-indicator="false"
+          />
+          <span class="progress-text">
+            {{ achievement.progress ?? 0 }} / {{ achievement.threshold }}
+          </span>
+        </div>
+
+        <div v-else-if="showBestSoFar" class="meta">
+          <span class="progress-text">
+            目标 ≤ {{ achievement.threshold }}
+          </span>
+          <span v-if="achievement.progress !== null" class="rate">
+            当前最好 {{ achievement.progress }}
+          </span>
+        </div>
+
+        <div v-else class="meta">
+          <span class="rate">仅 {{ achievement.unlock_rate }}% 的人获得</span>
+        </div>
+      </div>
+    </div>
+  </n-card>
+</template>
+
+<style scoped>
+.row {
+  display: flex;
+  gap: 12px;
+  align-items: flex-start;
+}
+.icon {
+  font-size: 32px;
+  line-height: 1;
+}
+.body {
+  flex: 1;
+  min-width: 0;
+}
+.title {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  font-weight: 600;
+}
+.desc {
+  margin-top: 4px;
+  font-size: 13px;
+  opacity: 0.75;
+}
+.meta {
+  margin-top: 8px;
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  font-size: 12px;
+  opacity: 0.65;
+}
+.meta :deep(.n-progress) {
+  flex: 1;
+}
+.progress-text {
+  white-space: nowrap;
+}
+.locked {
+  filter: grayscale(1);
+  opacity: 0.55;
+}
+.rare {
+  box-shadow: 0 0 12px rgba(125, 211, 252, 0.55);
+}
+</style>