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/CommentItem.tsx

@@ -493,7 +493,7 @@ const CommentItem: React.FC<CommentItemProps> = ({
                 </View>
                 {/* 显示回复内容（如果有文字） */}
                 {reply.content ? (
-                  <Text variant="body" color={colors.text.primary} style={styles.subReplyBody}>
+                  <Text variant="body" color={colors.text.primary} selectable style={styles.subReplyBody}>
                     {reply.content}
                   </Text>
                 ) : null}
@@ -625,7 +625,7 @@ const CommentItem: React.FC<CommentItemProps> = ({
               textStyle={[styles.text, { color: colors.text.primary }]}
             />
           ) : (
-            <Text variant="body" color={colors.text.primary} style={styles.text}>
+            <Text variant="body" color={colors.text.primary} selectable style={styles.text}>
               {comment.content}
             </Text>
           )}