feat(post): add post reference functionality with inline cards and suggestion search

Add support for referencing/quoting other posts within post content. Includes:
- New `post_ref` segment type with `PostRefSegmentData` interface for post references
- New `PostRefCard` component to display referenced posts inline
- Post suggestion search triggered by `#` in `PostMentionInput`
- Updated `PostContentRenderer` to render post reference segments
- Add `suggestPosts` and `recordRefClick` API methods in postService

Additional improvements:
- Add image gallery preview for user profile covers and avatars
- Make text selectable across CommentItem, PostContentRenderer, and PostDetailScreen
- Migrate FlatList to FlashList in PostDetailScreen and UserProfileScreen
- Add nestedScrollEnabled to CreatePostScreen
- Add clickable member avatars in GroupMembersScreen

src/components/business/PostRefCard.tsx

@@ -0,0 +1,124 @@
+import React, { useCallback } from 'react';
+import { View, TouchableOpacity, StyleSheet, ActivityIndicator } from 'react-native';
+import { MaterialCommunityIcons } from '@expo/vector-icons';
+import { useRouter } from 'expo-router';
+
+import Text from '../common/Text';
+import { useAppColors, spacing, borderRadius } from '../../theme';
+import type { PostRefSegmentData } from '../../types';
+
+interface PostRefCardProps {
+  data: PostRefSegmentData;
+  compact?: boolean;
+  onPress?: (postId: string) => void;
+}
+
+const PostRefCard: React.FC<PostRefCardProps> = ({ data, compact = false, onPress }) => {
+  const colors = useAppColors();
+  const router = useRouter();
+
+  const handlePress = useCallback(() => {
+    if (onPress) {
+      onPress(data.post_id);
+    } else {
+      router.push(`/post/${data.post_id}` as any);
+    }
+  }, [data.post_id, onPress, router]);
+
+  const isDeleted = data.status === 'deleted';
+  const isHidden = data.status === 'hidden';
+  const isUnavailable = isDeleted || isHidden || !data.accessible;
+  const authorName = data.author?.nickname || '';
+
+  if (isUnavailable) {
+    return (
+      <View
+        style={[
+          styles.container,
+          { backgroundColor: colors.background.default, borderColor: colors.divider },
+          compact && styles.containerCompact,
+        ]}
+      >
+        <MaterialCommunityIcons name="link-off" size={16} color={colors.text.hint} />
+        <Text style={[styles.unavailableText, { color: colors.text.hint }]} numberOfLines={1}>
+          {isDeleted ? '该帖子已删除' : isHidden ? '该帖子不可见' : '请登录后查看'}
+        </Text>
+      </View>
+    );
+  }
+
+  return (
+    <TouchableOpacity
+      style={[
+        styles.container,
+        { backgroundColor: colors.background.default, borderColor: colors.primary.light },
+        compact && styles.containerCompact,
+      ]}
+      onPress={handlePress}
+      activeOpacity={0.7}
+    >
+      <View style={[styles.iconWrap, { backgroundColor: colors.primary.light }]}>
+        <MaterialCommunityIcons name="file-document-outline" size={14} color={colors.primary.main} />
+      </View>
+      <View style={styles.contentWrap}>
+        <Text
+          style={[styles.title, { color: colors.text.primary }]}
+          numberOfLines={compact ? 1 : 2}
+        >
+          {data.title || '帖子'}
+        </Text>
+        {authorName ? (
+          <Text style={[styles.author, { color: colors.text.secondary }]} numberOfLines={1}>
+            @{authorName}
+          </Text>
+        ) : null}
+      </View>
+      <MaterialCommunityIcons name="chevron-right" size={16} color={colors.text.hint} />
+    </TouchableOpacity>
+  );
+};
+
+const styles = StyleSheet.create({
+  container: {
+    flexDirection: 'row',
+    alignItems: 'center',
+    borderWidth: 1,
+    borderRadius: borderRadius.md,
+    paddingVertical: spacing.sm,
+    paddingHorizontal: spacing.md,
+    marginTop: spacing.xs,
+    marginBottom: spacing.xs,
+  },
+  containerCompact: {
+    paddingVertical: spacing.xs,
+    paddingHorizontal: spacing.sm,
+  },
+  iconWrap: {
+    width: 24,
+    height: 24,
+    borderRadius: 4,
+    alignItems: 'center',
+    justifyContent: 'center',
+    marginRight: spacing.sm,
+  },
+  contentWrap: {
+    flex: 1,
+    justifyContent: 'center',
+  },
+  title: {
+    fontSize: 13,
+    fontWeight: '500',
+    lineHeight: 18,
+  },
+  author: {
+    fontSize: 11,
+    lineHeight: 14,
+    marginTop: 1,
+  },
+  unavailableText: {
+    fontSize: 13,
+    marginLeft: spacing.sm,
+  },
+});
+
+export default PostRefCard;