feat(challenges): 新增挑战详情页与排行榜及轮播卡片交互

- 重构挑战列表为横向轮播，支持多进行中的挑战
- 新增挑战详情页 /challenges/[id]/index 与排行榜 /challenges/[id]/leaderboard
- ChallengeProgressCard 支持小时级剩余时间显示
- 新增 ChallengeRankingItem 组件展示榜单项
- 排行榜支持分页加载、下拉刷新与错误重试
- 挑战卡片新增已结束角标与渐变遮罩
- 加入/退出挑战时展示庆祝动画与错误提示
- 统一背景渐变色与卡片阴影细节

services/challengesApi.ts

@@ -15,6 +15,8 @@ export type RankingItemDto = {
   avatar: string | null;
   metric: string;
   badge?: string;
+  todayReportedValue?: number;
+  todayTargetValue?: number;
 };
 
 export enum ChallengeType {
@@ -55,6 +57,13 @@ export type ChallengeDetailDto = ChallengeListItemDto & {
   userRank?: number;
 };
 
+export type ChallengeRankingsDto = {
+  total: number;
+  page: number;
+  pageSize: number;
+  items: RankingItemDto[];
+};
+
 export async function listChallenges(): Promise<ChallengeListItemDto[]> {
   return api.get<ChallengeListItemDto[]>('/challenges');
 }
@@ -75,3 +84,19 @@ export async function reportChallengeProgress(id: string, value?: number): Promi
   const body = value != null ? { value } : undefined;
   return api.post<ChallengeProgressDto>(`/challenges/${encodeURIComponent(id)}/progress`, body);
 }
+
+export async function getChallengeRankings(
+  id: string,
+  params?: { page?: number; pageSize?: number }
+): Promise<ChallengeRankingsDto> {
+  const searchParams = new URLSearchParams();
+  if (params?.page) {
+    searchParams.append('page', String(params.page));
+  }
+  if (params?.pageSize) {
+    searchParams.append('pageSize', String(params.pageSize));
+  }
+  const query = searchParams.toString();
+  const url = `/challenges/${encodeURIComponent(id)}/rankings${query ? `?${query}` : ''}`;
+  return api.get<ChallengeRankingsDto>(url);
+}