fix: RoutePanel 측점 선형 위아래 반전 수정

kmToY 함수를 반전(1 - ratio)하여 높은 km값이 아래, 낮은 km값이 위에 오도록 수정.
visibleRange 초록 박스 top/bottom도 함께 교정.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/src/components/overlay/RoutePanel.tsx

@@ -223,7 +223,7 @@ export default function RoutePanel({ currentTime, visible, onSeek }: RoutePanelP
   ];
   const minKm = Math.min(...allKms);
   const maxKm = Math.max(...allKms);
-  const kmToY = (km: number) => ((km - minKm) / (maxKm - minKm)) * 100;
+  const kmToY = (km: number) => (1 - (km - minKm) / (maxKm - minKm)) * 100;
 
   return (
     <div
@@ -289,8 +289,8 @@ export default function RoutePanel({ currentTime, visible, onSeek }: RoutePanelP
           style={{
             left: 30,
             right: 4,
-            top: `${kmToY(visibleRange.minKm)}%`,
-            bottom: `${100 - kmToY(visibleRange.maxKm)}%`,
+            top: `${kmToY(visibleRange.maxKm)}%`,
+            bottom: `${100 - kmToY(visibleRange.minKm)}%`,
             border: '1px solid rgba(74,222,128,0.7)',
             background: 'rgba(74,222,128,0.08)',
           }}