fix: Chakra v3のIcon asプロパティをchildren方式に修正

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: yn1323

src/routes/_unregistered/shifts.view.tsx

@@ -90,7 +90,9 @@ function ShiftViewRoute() {
       <StaffLayout shopName="シフト閲覧">
         <Flex flex={1} align="center" justify="center" px={8}>
           <VStack gap={4}>
-            <Icon as={LuTriangleAlert} boxSize={12} color="orange.500" />
+            <Icon boxSize={12} color="orange.500">
+              <LuTriangleAlert />
+            </Icon>
             <Text fontSize="lg" fontWeight="semibold" textAlign="center">
               アクセス制限中
             </Text>