feat(auth): enhance login error handling with detailed error code mapping

- Add backend error_code support (INVALID_CREDENTIALS, USER_BANNED, etc.)
- Improve network error detection with code=0 fallback
- Add granular HTTP status code handling (400, 401, 403, 429, 5xx)
- Update LoginScreen to display authStore error or generic message
- Include notification service improvements:
  - Keep JPush connection alive in background via setKeepLongConnInBackground
  - Add manual sound/vibration for local notifications via preferences
- Fix SearchScreen layout by accounting for floating tab bar and safe area

src/screens/auth/LoginScreen.tsx

@@ -107,12 +107,11 @@ export const LoginScreen: React.FC = () => {
     try {
       const success = await login({ username, password });
       if (!success) {
-        if (!useAuthStore.getState().error) {
-          showPrompt({ title: '登录失败', message: '请检查用户名和密码', type: 'error' });
-        }
+        const errorMsg = useAuthStore.getState().error || '登录失败，请稍后重试';
+        showPrompt({ title: '登录失败', message: errorMsg, type: 'error' });
       }
     } catch (error: any) {
-      showPrompt({ title: '登录失败', message: error.message || '请检查用户名和密码', type: 'error' });
+      showPrompt({ title: '登录失败', message: error.message || '登录失败，请稍后重试', type: 'error' });
     } finally {
       setLoading(false);
     }

src/screens/home/SearchScreen.tsx

@@ -13,7 +13,7 @@ import {
   ScrollView,
   RefreshControl,
 } from 'react-native';
-import { SafeAreaView } from 'react-native-safe-area-context';
+import { SafeAreaView, useSafeAreaInsets } from 'react-native-safe-area-context';
 import { useRouter } from 'expo-router';
 import { MaterialCommunityIcons } from '@expo/vector-icons';
 import { spacing, fontSizes, borderRadius, useAppColors, type AppColors } from '../../theme';
@@ -30,6 +30,8 @@ import { useCursorPagination } from '../../hooks/useCursorPagination';
 
 const TABS = ['帖子', '用户'];
 const DEFAULT_PAGE_SIZE = 20;
+// 与 TabsLayout 中的常量保持一致：tabBarHeight 56 + 上下浮动间距 12*2
+const FLOATING_TAB_BAR_HEIGHT = 56 + 12 * 2;
 
 type SearchType = 'posts' | 'users';
 
@@ -41,6 +43,7 @@ export const SearchScreen: React.FC<SearchScreenProps> = ({ onBack }) => {
   const colors = useAppColors();
   const styles = useMemo(() => createSearchScreenStyles(colors), [colors]);
   const router = useRouter();
+  const insets = useSafeAreaInsets();
   const { searchHistory: history, addSearchHistory, clearSearchHistory } = useUserStore();
   
   // 使用响应式 hook
@@ -73,6 +76,9 @@ export const SearchScreen: React.FC<SearchScreenProps> = ({ onBack }) => {
     '4xl': 1200,
   });
   
+  // 底部预留空间：悬浮 TabBar 高度 + 底部安全区 + 间距
+  const listBottomInset = FLOATING_TAB_BAR_HEIGHT + insets.bottom + spacing.md;
+
   const [searchText, setSearchText] = useState('');
   const [activeIndex, setActiveIndex] = useState(0);
   const [hasSearched, setHasSearched] = useState(false);
@@ -238,7 +244,7 @@ export const SearchScreen: React.FC<SearchScreenProps> = ({ onBack }) => {
       return (
         <ScrollView 
           showsVerticalScrollIndicator={false}
-          contentContainerStyle={{ paddingBottom: responsivePadding }}
+          contentContainerStyle={{ paddingBottom: listBottomInset }}
           refreshControl={
             <RefreshControl
               refreshing={isRefreshing}
@@ -287,7 +293,7 @@ export const SearchScreen: React.FC<SearchScreenProps> = ({ onBack }) => {
           />
         )}
         keyExtractor={item => item.id}
-        contentContainerStyle={{ paddingBottom: responsivePadding }}
+        contentContainerStyle={{ paddingBottom: listBottomInset }}
         showsVerticalScrollIndicator={false}
         refreshControl={
           <RefreshControl
@@ -323,7 +329,7 @@ export const SearchScreen: React.FC<SearchScreenProps> = ({ onBack }) => {
       return (
         <ScrollView 
           showsVerticalScrollIndicator={false}
-          contentContainerStyle={{ paddingBottom: responsivePadding }}
+          contentContainerStyle={{ paddingBottom: listBottomInset }}
         >
           <ResponsiveGrid
             columns={{ xs: 1, sm: 2, md: 2, lg: 3, xl: 3, '2xl': 4, '3xl': 4, '4xl': 5 }}
@@ -412,7 +418,7 @@ export const SearchScreen: React.FC<SearchScreenProps> = ({ onBack }) => {
           </TouchableOpacity>
         )}
         keyExtractor={item => item.id}
-        contentContainerStyle={{ paddingVertical: responsiveGap }}
+        contentContainerStyle={{ paddingVertical: responsiveGap, paddingBottom: listBottomInset }}
         showsVerticalScrollIndicator={false}
         ListFooterComponent={userLoading ? <Loading size="sm" /> : null}
       />