fix: 统一修复所有屏幕的安全区域问题

- 有 header 的屏幕使用 edges={['bottom']}（React Navigation 自动处理顶部）
- 没有 header 的屏幕使用 edges={['top', 'bottom']}（需要自己处理顶部）
- 修复了以下屏幕：
  - HomeScreen: edges={['bottom']} → ['top', 'bottom']
  - MessageListScreen: edges={['top']} → ['top', 'bottom']
  - ScheduleScreen: edges={['top']} → ['top', 'bottom']
  - ProfileScreen: edges={['top', 'bottom']} ✓ 已正确
  - PostDetailScreen: 空状态添加 edges={['bottom']}
  - UserScreen: 空状态添加 edges={['bottom']}
  - NotificationsScreen: edges={[]} → ['bottom']
  - SearchScreen: edges={['left', 'right']} → ['bottom']
  - BlockedUsersScreen: 加载状态添加 edges={['bottom']}
  - GroupInfoScreen: edges={['bottom']} ✓ 已正确
  - PrivateChatInfoScreen: 加载状态添加 edges={['bottom']}

src/screens/message/GroupInfoScreen.tsx

@@ -534,7 +534,7 @@ const GroupInfoScreen: React.FC = () => {
 
   if (loading) {
     return (
-      <SafeAreaView style={styles.container}>
+      <SafeAreaView style={styles.container} edges={['bottom']}>
         <Loading />
       </SafeAreaView>
     );
@@ -542,7 +542,7 @@ const GroupInfoScreen: React.FC = () => {
 
   if (!group) {
     return (
-      <SafeAreaView style={styles.container}>
+      <SafeAreaView style={styles.container} edges={['bottom']}>
         <View style={styles.errorContainer}>
           <Text variant="body" color={colors.text.secondary}>
             群组信息不存在

src/screens/message/MessageListScreen.tsx

@@ -931,7 +931,7 @@ export const MessageListScreen: React.FC = () => {
   // 桌面端双栏布局
   if (isWideScreen && !isSearchMode) {
     return (
-      <SafeAreaView style={styles.container} edges={['top']}>
+      <SafeAreaView style={styles.container} edges={['top', 'bottom']}>
         <View style={styles.desktopContainer}>
           {/* 左侧会话列表 */}
           <View style={[styles.sidebar, { width: sidebarWidth }]}>
@@ -966,7 +966,7 @@ export const MessageListScreen: React.FC = () => {
   }
 
   return (
-    <SafeAreaView style={styles.container} edges={['top']}>
+    <SafeAreaView style={styles.container} edges={['top', 'bottom']}>
       {showNotifications ? (
         // 显示系统通知页面，传入 onBack 回调
         <NotificationsScreen onBack={() => setShowNotifications(false)} />

src/screens/message/NotificationsScreen.tsx

@@ -372,7 +372,7 @@ export const NotificationsScreen: React.FC<{ onBack?: () => void }> = ({ onBack
   // 如果还未hydrated，显示加载占位符，避免竞态条件导致的渲染问题
   if (!isHydrated) {
     return (
-      <SafeAreaView style={styles.container} edges={[]}>
+      <SafeAreaView style={styles.container} edges={['bottom']}>
         <View style={styles.loadingContainer}>
           <ActivityIndicator size="large" color={colors.primary.main} />
         </View>
@@ -381,7 +381,7 @@ export const NotificationsScreen: React.FC<{ onBack?: () => void }> = ({ onBack
   }
 
   return (
-    <SafeAreaView style={styles.container} edges={[]}>
+    <SafeAreaView style={styles.container} edges={['bottom']}>
       {isWideScreen ? (
         <ResponsiveContainer maxWidth={containerMaxWidth}>
           {/* 头部 - 大屏模式下隐藏返回按钮 */}

src/screens/message/PrivateChatInfoScreen.tsx

@@ -307,7 +307,7 @@ const PrivateChatInfoScreen: React.FC = () => {
 
   if (loading) {
     return (
-      <SafeAreaView style={styles.container}>
+      <SafeAreaView style={styles.container} edges={['bottom']}>
         <Loading />
       </SafeAreaView>
     );