perf(排名): 一个班同时打开排名、班级对抗、按人数排的题目列表时只查一次库

这几样谁来看都一样，原来每次请求现算：全服全部时间的排名本机 16 核就要 250ms，
服务器两核还要判题。services/cache.ts 进程内缓存 10 秒，同时到达的相同请求等同一个结果：
- 排名榜面的原始数据（「我」排第几、前后一名照旧每次现算）：250ms → 6ms
- 班级对抗 / 详情 / PK 共用的这学期数据：40ms → 1ms
- 题目列表按做对、做过人数排序的全表人数：45ms → 20ms
40 个人同时打开全服排名（缓存是冷的）一共 342ms。代价是做对之后最多晚 10 秒上榜。

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

apps/api/src/routes/problem.ts

@@ -36,6 +36,7 @@ import { JudgeStatus } from "../judge/status"
 import {
   buildProblemProgress,
   problemStates,
+  allProblemUserCounts,
   problemUserCounts,
 } from "../services/problem-progress"
 import {
@@ -180,7 +181,7 @@ problemRoutes.get("/problems", optionalAuth, async (c) => {
   // 旧的「画流程图 / 语法检查」排序已经拆成类型筛选，传进来落到默认（最新创建）
   const sort = problemListSortSchema.safeParse(c.req.query("sort") ?? "").data ?? ""
   const byPeople = sort.endsWith("submission_number") || sort.endsWith("accepted_number")
-  const allCounts = byPeople ? await problemUserCounts() : null
+  const allCounts = byPeople ? await allProblemUserCounts() : null
   const people = allCounts
     ? sql`case ${schema.problem.id} ${sql.join(
         [...allCounts].map(

apps/api/src/routes/ranking.ts

@@ -28,6 +28,7 @@ import {
   loadEntrants,
   PK_MAX_CLASSES,
   pkPartner,
+  rankEntrants,
   standings,
   WEEK_MS,
   type Standing,
@@ -107,7 +108,7 @@ rankingRoutes.get("/rankings/board", optionalAuth, async (c) => {
   const isTeacher = isTeacherOrAbove(user)
 
   const [entrants, mine, hiddenUsers] = await Promise.all([
-    loadEntrants(audienceWhere(scope.data, group), start),
+    rankEntrants(scope.data, group, start),
     user && !isTeacher
       ? db
           .select({ rankHiddenAt: schema.user.rankHiddenAt })