60s 轮询扩展：跑道曲线 + 站点观测同步刷新

原来只轮询 summary 拿 current.temp 更新数字。
现在同时 fetch detail?depth=full 合并 amos/runway_plate_history/
airport_primary_today_obs 等字段，跑道曲线和站点线每 60s 刷新。
后端 CITY_FULL_CACHE_TTL_SEC=60 保证轻量命中缓存。

frontend/components/dashboard/scan-terminal/LoadingSignal.tsx

@@ -11,21 +11,60 @@ export function LoadingSignal({
 }) {
   return (
     <div
-      className={clsx("scan-loading-signal", compact && "compact")}
+      className={clsx(
+        "flex flex-col items-center justify-center text-center select-none",
+        compact ? "p-4 gap-2 w-full max-w-[280px]" : "p-6 gap-4 w-full max-w-[360px]"
+      )}
       role="status"
       aria-live="polite"
     >
-      <div className="scan-loading-spinner-wrapper" aria-hidden="true">
-        <div className="scan-loading-spinner-ring" />
-        <img
-          src="/apple-touch-icon.png"
-          alt="PolyWeather"
-          className="scan-loading-spinner-logo"
-        />
+      <div 
+        className={clsx(
+          "relative flex items-center justify-center rounded-full shrink-0",
+          compact ? "w-16 h-16" : "w-24 h-24"
+        )} 
+        aria-hidden="true"
+      >
+        {/* Background Track Ring */}
+        <div className="absolute inset-0 rounded-full border-[3px] border-slate-200/80 dark:border-slate-800" />
+        
+        {/* Active Spinning Ring */}
+        <div className="absolute inset-0 rounded-full border-[3px] border-transparent border-t-blue-500 border-r-blue-400 animate-spin" />
+        
+        {/* Centered Rounded Logo Card */}
+        <div 
+          className={clsx(
+            "absolute bg-white dark:bg-slate-900 rounded-xl flex items-center justify-center shadow-sm border border-slate-100/80 dark:border-slate-800/80",
+            compact ? "w-10 h-10" : "w-14 h-14"
+          )}
+        >
+          <img
+            src="/apple-touch-icon.png"
+            alt="PolyWeather Logo"
+            className={clsx(
+              "object-contain rounded-lg",
+              compact ? "w-7 h-7" : "w-10 h-10"
+            )}
+          />
+        </div>
       </div>
-      <div className="scan-loading-copy-block">
-        <strong>{title}</strong>
-        {description ? <span>{description}</span> : null}
+      
+      {/* Text Copy */}
+      <div className="flex flex-col items-center gap-1">
+        <strong className={clsx(
+          "font-bold text-slate-800 dark:text-slate-100",
+          compact ? "text-xs" : "text-sm"
+        )}>
+          {title}
+        </strong>
+        {description && (
+          <span className={clsx(
+            "text-slate-500 dark:text-slate-400 leading-normal",
+            compact ? "text-[10px] max-w-[200px]" : "text-xs max-w-[280px]"
+          )}>
+            {description}
+          </span>
+        )}
       </div>
     </div>
   );