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 .

web/analysis_service.py

@@ -2054,6 +2054,7 @@ def _analyze(
     else:
         peak_status = "before"
 
+    lgbm_val = None
     if current_forecasts and deb_val is not None:
         lgbm_val, _ = predict_lgbm_daily_high(
             city_name=city,
@@ -2069,11 +2070,8 @@ def _analyze(
             peak_status=peak_status,
         )
         if lgbm_val is not None:
-            current_forecasts["LGBM"] = lgbm_val
-            blended, winfo = calculate_dynamic_weights(city, current_forecasts)
-            if blended is not None:
-                deb_val = blended
-                deb_weights = winfo
+            # LGBM is kept as an independent reference, not fed back into DEB
+            # to avoid circular dependency (DEB → LGBM training → DEB)
 
     deviation_monitor = _build_deviation_monitor(
         current_temp=cur_temp,
@@ -2496,6 +2494,7 @@ def _analyze(
         "multi_model": {k: v for k, v in current_forecasts.items() if v is not None},
         "multi_model_daily": multi_model_daily,
         "deb": {"prediction": deb_val, "weights_info": deb_weights},
+        "lgbm": {"prediction": lgbm_val},
         "deviation_monitor": deviation_monitor,
         "ensemble": ens_data,
         "probabilities": {

web/scan_terminal_service.py

@@ -88,8 +88,8 @@ def _env_int(
 
 
 SCAN_TERMINAL_PAYLOAD_TTL_SEC = max(
-    5,
-    int(os.getenv("POLYWEATHER_SCAN_TERMINAL_PAYLOAD_TTL_SEC", "30")),
+    10,
+    int(os.getenv("POLYWEATHER_SCAN_TERMINAL_PAYLOAD_TTL_SEC", "120")),
 )
 SCAN_TERMINAL_BUILD_TIMEOUT_SEC = max(
     8,