refactor(ui): implement custom header system and unify screen layouts

Refactor the navigation and header strategy by replacing native stack headers with a custom `SimpleHeader` component across most profile and detail screens. This provides a more consistent UI/UX and better control over layout behavior.

- Implement `SimpleHeader` component in `src/components/common`.
- Disable native header rendering in `app/(app)/(tabs)/profile/_layout.tsx` and `app/_layout.tsx`.
- Update profile sub-screens to use `SimpleHeader` and `StatusBar` from `expo-status-bar`.
- Refactor `PostDetailScreen` to use a custom header implementation for better integration with the post author information.
- Update `UserScreen` to wrap content in `SafeAreaView` with the new header.
- Adjust `AppBackButton` to support transparent backgrounds.

src/screens/profile/VerificationSettingsScreen.tsx

@@ -14,8 +14,10 @@ import {
   Alert,
   ActivityIndicator,
 } from 'react-native';
+import { StatusBar } from 'expo-status-bar';
 import { SafeAreaView } from 'react-native-safe-area-context';
 import { useRouter } from 'expo-router';
+import { SimpleHeader } from '../../components/common';
 import { MaterialCommunityIcons } from '@expo/vector-icons';
 import { useAppColors, type AppColors } from '../../theme';
 import {
@@ -91,7 +93,9 @@ export const VerificationSettingsScreen: React.FC = () => {
 
   if (loading && !status) {
     return (
-      <SafeAreaView style={styles.container}>
+      <SafeAreaView style={styles.container} edges={['top', 'bottom']}>
+        <StatusBar style="auto" />
+        <SimpleHeader title="身份认证" onBack={() => router.back()} />
         <View style={styles.loadingContainer}>
           <ActivityIndicator size="large" color={colors.primary.main} />
         </View>
@@ -104,7 +108,9 @@ export const VerificationSettingsScreen: React.FC = () => {
   const identityText = IDENTITY_TEXT[status?.identity || 'general'];
 
   return (
-    <SafeAreaView style={styles.container}>
+    <SafeAreaView style={styles.container} edges={['top', 'bottom']}>
+      <StatusBar style="auto" />
+      <SimpleHeader title="身份认证" onBack={() => router.back()} />
       <ScrollView
         contentContainerStyle={styles.scrollContent}
         showsVerticalScrollIndicator={false}