修复数据链路 P0 瓶颈：缓存炸弹、Context 重渲染、LGBM 循环、TTL 不匹配

P0-1 sessionStorage 限制：
- writeCityDetailCacheBundle 只保留最近 3 个城市的详情
- 避免 3-10MB JSON 序列化阻塞主线程

P0-2 Context 拆分：
- 新增 CityDetailsContext 独立管理 cityDetailsByName 变更
- 新增 useCityDetails hook，只订阅详情的组件不再因 cities/proAccess 变化重渲染
- DashboardStoreContext 保持不变，向后兼容

P0-3 扫描终端 TTL：
- SCAN_TERMINAL_PAYLOAD_TTL_SEC 30s → 120s
- 匹配 ThreadPoolExecutor(4) x 60 城的实际重算耗时

P0-4 LGBM 循环依赖：
- LGBM 预测值不再作为 DEB 输入参与权重计算
- 保留为独立参考字段 lgbm.prediction 输出给前端展示
- 消除 DEB → LGBM 训练 → DEB 的循环

新增 docs/data-architecture-review.md 完整数据链路审查报告

Tested: npx tsc --noEmit, python -m ruff check .

frontend/hooks/useDashboardStore.tsx

@@ -73,6 +73,12 @@ interface DashboardStoreValue extends DashboardState {
 }
 
 const DashboardStoreContext = createContext<DashboardStoreValue | null>(null);
+const CityDetailsContext = createContext<{
+  cityDetailsByName: Record<string, CityDetail>;
+  cityDetailMetaByName: Record<string, { cachedAt: number; revision: string }>;
+  citySummariesByName: Record<string, CitySummary>;
+  loadingState: LoadingState;
+} | null>(null);
 
 function getInitialLoadingState(): LoadingState {
   return {
@@ -1520,9 +1526,16 @@ export function DashboardStoreProvider({
     ],
   );
 
+  const cityDetailsValue = useMemo(
+    () => ({ cityDetailsByName, cityDetailMetaByName, citySummariesByName, loadingState }),
+    [cityDetailsByName, cityDetailMetaByName, citySummariesByName, loadingState],
+  );
+
   return (
     <DashboardStoreContext.Provider value={value}>
-      {children}
+      <CityDetailsContext.Provider value={cityDetailsValue}>
+        {children}
+      </CityDetailsContext.Provider>
     </DashboardStoreContext.Provider>
   );
 }
@@ -1537,6 +1550,16 @@ export function useDashboardStore() {
   return context;
 }
 
+export function useCityDetails() {
+  const context = useContext(CityDetailsContext);
+  if (!context) {
+    throw new Error(
+      "useCityDetails must be used within DashboardStoreProvider",
+    );
+  }
+  return context;
+}
+
 export function useCityData(name?: string | null) {
   const store = useDashboardStore();
   const key = name || store.selectedCity;

frontend/lib/dashboard-client.ts

@@ -542,15 +542,19 @@ export const dashboardClient = {
     meta: Record<string, CityCacheMeta>,
   ) {
     if (!isClient()) return;
+    // Keep only the 3 most-recently-accessed cities to prevent sessionStorage bloat
+    const MAX_CACHED_CITIES = 3;
+    const allEntries = Object.entries(details).map(([cityName, detail]) => ({
+      cityName,
+      cachedAt: meta[cityName]?.cachedAt || 0,
+      detail,
+      revision: meta[cityName]?.revision || getCityRevision(detail),
+    }));
+    const topEntries = allEntries
+      .sort((a, b) => b.cachedAt - a.cachedAt)
+      .slice(0, MAX_CACHED_CITIES);
     const entries = Object.fromEntries(
-      Object.entries(details).map(([cityName, detail]) => [
-        cityName,
-        {
-          cachedAt: meta[cityName]?.cachedAt || Date.now(),
-          detail,
-          revision: meta[cityName]?.revision || getCityRevision(detail),
-        },
-      ]),
+      topEntries.map((e) => [e.cityName, { cachedAt: e.cachedAt, detail: e.detail, revision: e.revision }]),
     );
     window.sessionStorage.setItem(
       CACHE_KEY,