Fix safe area insets for iPhone using CSS custom properties

src/app/page.tsx

@@ -219,7 +219,7 @@ export default function Home() {
   }
 
   return (
-    <div className="min-h-screen bg-gradient-to-b from-slate-50 to-slate-100 dark:from-slate-900 dark:to-slate-800 pb-24 md:pb-0" style={{ paddingBottom: 'calc(6rem + env(safe-area-inset-bottom))' }}>
+    <div className="min-h-screen bg-gradient-to-b from-slate-50 to-slate-100 dark:from-slate-900 dark:to-slate-800 md:pb-0" style={{ paddingBottom: 'calc(6rem + var(--safe-area-inset-bottom))' }}>
       <ReminderBanner userEmail={user.email || undefined} />
       <BottomNav activeTab={activeTab} onTabChange={setActiveTab} />