라이트 테마 강제 적용 + surface 토큰 + 텍스트 대비 개선

- dark: 클래스를 class 기반으로 전환 (다크모드 비활성화)
- color-scheme: light 강제
- surface 색상 토큰 추가 (카드/패널용)
- 리스트/사이드바 배경 bg-surface로 통일
- 텍스트 대비 강화 (gray-400 → gray-500/700)

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

frontend/src/components/MapView.tsx

@@ -231,7 +231,7 @@ export default function MapView({ restaurants, selected, onSelectRestaurant, onB
       {onMyLocation && (
         <button
           onClick={onMyLocation}
-          className="absolute top-2 right-2 w-9 h-9 bg-white dark:bg-gray-900 rounded-lg shadow-md flex items-center justify-center text-gray-600 dark:text-gray-300 hover:text-brand-500 dark:hover:text-brand-400 transition-colors z-10"
+          className="absolute top-2 right-2 w-9 h-9 bg-surface rounded-lg shadow-md flex items-center justify-center text-gray-600 dark:text-gray-300 hover:text-brand-500 dark:hover:text-brand-400 transition-colors z-10"
           title="내 위치"
         >
           <svg viewBox="0 0 24 24" className="w-5 h-5 fill-current">
@@ -240,7 +240,7 @@ export default function MapView({ restaurants, selected, onSelectRestaurant, onB
         </button>
       )}
       {channelNames.length > 0 && (
-        <div className="absolute bottom-2 left-2 bg-white/90 dark:bg-gray-900/90 backdrop-blur-sm rounded-lg shadow px-2.5 py-1.5 flex flex-wrap gap-x-3 gap-y-1 text-[11px] z-10">
+        <div className="absolute bottom-2 left-2 bg-surface/90 backdrop-blur-sm rounded-lg shadow px-2.5 py-1.5 flex flex-wrap gap-x-3 gap-y-1 text-[11px] z-10">
           {channelNames.map((ch) => (
             <div key={ch} className="flex items-center gap-1">
               <span