feat(api): 比赛上下文与联赛列表改公开只读(P1-2/P1-3)

- GET /matches/{id}/context 移除 require_admin:公开站详情页「近况/交锋」
  数据来源,匿名 401 会导致前端静默空态;响应结构不变,不触发 LLM
- GET /leagues 改公开只读:公开站联赛筛选动态加载;仅返回
  id/code/name/country 四个展示字段,不含配置或密钥信息
- 前端新增 useLeagues hook:优先请求 /api/v1/leagues,失败/空回退
  本地五大联赛常量(已知代码保留中文标签,新联赛按 API 名称追加)
- 新增 tests/test_public_readonly_api.py(6 项):匿名 200/404、响应形状、
  路由依赖声明检查(matches 路由无 require_admin)+ 判别力守卫
  (ingest 路由必须检出 require_admin,防检测器恒真)

frontend/src/pages/Matches.tsx

@@ -15,13 +15,16 @@ import { fetchMatchDetail, fetchMatchContext } from '../admin/dal'
 import type { MatchDetailOut, MatchContextOut } from '../admin/types'
 import { useMatchesList } from './matches/hooks/useMatchesList'
 import { useMatchPredict } from './matches/hooks/useMatchPredict'
+import { useLeagues } from './matches/hooks/useLeagues'
 import { PredictModal } from './matches/components/MatchPredictPanel'
 import { MatchRow } from './matches/components/MatchDetailSection'
 import { Spinner, SkeletonRows, Switch, formatDateHeader, groupByDate, withinNext3Days } from './matches/ui'
-import { LEAGUES, type Match } from './matches/types'
+import { type Match } from './matches/types'
 
 export default function Matches() {
   const [error, setError] = useState<string | null>(null)  // 列表与预测共用(拆分前即如此)
+  // P1-3: 联赛列表优先请求 /api/v1/leagues,失败/空回退本地五大联赛常量
+  const leagues = useLeagues()
   const {
     league, setLeague,
     status, setStatus,
@@ -58,7 +61,7 @@ export default function Matches() {
   }, [])
   const scrollToTop = () => window.scrollTo({ top: 0, behavior: 'smooth' })
 
-  const leagueName = LEAGUES.find(l => l.code === league)?.name ?? league
+  const leagueName = leagues.find(l => l.code === league)?.name ?? league
 
   /** 未开赛默认仅展示未来 3 天;其余状态展示全部。showAllUpcoming=true 时展开全部。 */
   const isScheduledView = status === 'scheduled'
@@ -91,7 +94,7 @@ export default function Matches() {
     <div className="space-y-5">
       {/* ── 联赛版面切换 ── */}
       <nav className="flex items-center gap-6 overflow-x-auto border-b border-ink-900" aria-label="联赛">
-        {LEAGUES.map(l => (
+        {leagues.map(l => (
           <button
             key={l.code}
             onClick={() => setLeague(l.code)}