fix: 페이지 헤더 lead 문단을 컨테이너 전체 폭으로 확장

Author: 9bow

src/pages/AboutPage.tsx

@@ -300,7 +300,7 @@ function PageHeader({
           fontSize: { xs: 16, md: 18 },
           lineHeight: 1.65,
           color: 'var(--fg-2)',
-          maxWidth: 640,
+          width: '100%',
         }}
       >
         {lead}

src/pages/GuidePage.tsx

@@ -318,7 +318,7 @@ function PageHeader({
       >
         {title}
       </Typography>
-      <Typography sx={{ fontSize: { xs: 16, md: 18 }, lineHeight: 1.65, color: 'var(--fg-2)', maxWidth: 640 }}>
+      <Typography sx={{ fontSize: { xs: 16, md: 18 }, lineHeight: 1.65, color: 'var(--fg-2)', width: '100%' }}>
         {lead}
       </Typography>
     </Box>