Shift default prewarm cities from US to Asia and Europe

docs/CONFIGURATION_ZH.md

@@ -146,6 +146,14 @@ PolyWeather 的环境变量很多，但不是所有变量都属于同一层级
 - 先用默认值
 - 出现性能或运维问题时再调
 
+当前默认预热名单优先覆盖：
+
+- 亚洲：Shanghai、Beijing、Shenzhen、Wuhan、Chengdu、Chongqing、Hong Kong、Taipei、Singapore、Tokyo、Seoul、Busan
+- 中东：Ankara、Istanbul
+- 欧洲：London、Paris、Madrid
+
+默认不再包含美国城市；如果线上 `.env` 已手动设置 `POLYWEATHER_PREWARM_CITIES`，则会以你的显式配置为准。
+
 ### 4.4 L4：敏感项
 
 这些变量不应写进公开文档截图，也不应提交到仓库。
@@ -285,7 +293,7 @@ POLYWEATHER_GROQ_COMMENTARY_CACHE_TTL_SEC=1800
 POLYWEATHER_DASHBOARD_PREWARM_ENABLED=true
 POLYWEATHER_PREWARM_INTERVAL_SEC=300
 POLYWEATHER_PREWARM_JITTER_SEC=20
-POLYWEATHER_PREWARM_CITIES=ankara,istanbul,shanghai,beijing,shenzhen,wuhan,chengdu,chongqing,hong kong,taipei,london,paris,new york,los angeles
+POLYWEATHER_PREWARM_CITIES=ankara,istanbul,shanghai,beijing,shenzhen,wuhan,chengdu,chongqing,hong kong,taipei,singapore,tokyo,seoul,busan,london,paris,madrid
 POLYWEATHER_PREWARM_INCLUDE_DETAIL=true
 POLYWEATHER_PREWARM_INCLUDE_MARKET=true
 POLYWEATHER_PREWARM_FORCE_REFRESH=false