今日实测最高改为从 airport_obs_log 取值，延长保留至 24h

不再依赖 city_weather.current.max_so_far（可能来自 METAR 等非机场源），
直接从 airport_obs_log 的机场站点观测历史中计算当日最高温及时间。
obs_log 保留期从 2h 延长到 24h 以支撑跨天查询。

Tested: pytest 176 passed, ruff check 通过

src/database/db_manager.py

@@ -1861,7 +1861,7 @@ class DBManager:
                  temp_c, wind_kt, pressure_hpa, str(obs_time)),
             )
             conn.execute(
-                "DELETE FROM airport_obs_log WHERE created_at < datetime('now', '-2 hours')"
+                "DELETE FROM airport_obs_log WHERE created_at < datetime('now', '-24 hours')"
             )
             conn.commit()
 

src/utils/telegram_push.py

@@ -763,14 +763,40 @@ def _build_airport_status_message(
         lines.append(f"当前实测：{station_temp:.1f}°C")
     if deb_pred is not None:
         lines.append(f"今日DEB预报最高：{deb_pred:.1f}°C")
-    max_so_far = current.get("max_so_far")
+    max_so_far, max_temp_time = _get_airport_daily_high(city)
-    max_temp_time = current.get("max_temp_time")
     if max_so_far is not None:
         time_str = f"（{max_temp_time}）" if max_temp_time else ""
         lines.append(f"今日实测最高：{max_so_far:.1f}°C{time_str}")
     return "\n".join(lines)
 
 
+def _get_airport_daily_high(city: str):
+    """Get today's observed high from airport_obs_log for this city."""
+    icao = HIGH_FREQ_AIRPORT_ICAO.get(city, "")
+    if not icao:
+        return None, None
+    try:
+        from src.database.db_manager import DBManager
+        db = DBManager()
+        obs = db.get_airport_obs_recent(icao, minutes=1440)  # last 24h
+        if not obs:
+            return None, None
+        best = max(obs, key=lambda r: r.get("temp_c") or -999)
+        temp_c = best.get("temp_c")
+        obs_time = best.get("obs_time") or ""
+        if temp_c is None:
+            return None, None
+        try:
+            from datetime import datetime
+            dt = datetime.fromisoformat(str(obs_time))
+            time_str = dt.strftime("%H:%M")
+        except Exception:
+            time_str = str(obs_time)[:5] if obs_time else ""
+        return round(float(temp_c), 1), time_str
+    except Exception:
+        return None, None
+
+
 # Per-city push interval matching native data refresh rate (seconds)
 _AIRPORT_PUSH_INTERVAL = {
     "seoul": 60,       # AMOS 1-min