feat(posts): add post reference/internal linking functionality

Add support for referencing other posts within messages through a new post_ref segment type. Includes new PostReference model to track relationships, PostRefService for processing references, and new endpoints for post suggestions, related posts, and reference click tracking.

internal/dto/segment.go

@@ -145,6 +145,17 @@ func NewLinkSegment(url, title, description, image string) model.MessageSegment
 	}
 }
 
+// NewPostRefSegment 创建帖子内链Segment
+func NewPostRefSegment(postID, title string) model.MessageSegment {
+	return model.MessageSegment{
+		Type: string(SegmentTypePostRef),
+		Data: map[string]any{
+			"post_id": postID,
+			"title":   title,
+		},
+	}
+}
+
 // ExtractVoteSegmentData 从消息链中提取投票Segment数据
 func ExtractVoteSegmentData(segments model.MessageSegments) *VoteSegmentData {
 	for _, segment := range segments {
@@ -227,6 +238,12 @@ func ExtractTextContentFromModel(segments model.MessageSegments) string {
 			}
 		case "vote":
 			result += "[投票]"
+		case "post_ref":
+			if title, ok := segment.Data["title"].(string); ok && title != "" {
+				result += fmt.Sprintf("[帖子:%s]", title)
+			} else {
+				result += "[帖子引用]"
+			}
 		}
 	}
 	return result
@@ -256,6 +273,28 @@ func ExtractMentionedUsers(segments model.MessageSegments) []string {
 	return userIDs
 }
 
+// ExtractReferencedPosts 从消息链中提取所有被引用的帖子ID
+func ExtractReferencedPosts(segments model.MessageSegments) []string {
+	var postIDs []string
+	seen := make(map[string]bool)
+
+	for _, segment := range segments {
+		if segment.Type == string(SegmentTypePostRef) {
+			postID, _ := segment.Data["post_id"].(string)
+			if postID != "" && !seen[postID] {
+				postIDs = append(postIDs, postID)
+				seen[postID] = true
+			}
+		}
+	}
+	return postIDs
+}
+
+// HasPostRefSegment 检查消息链中是否包含帖子引用
+func HasPostRefSegment(segments model.MessageSegments) bool {
+	return HasSegmentType(segments, SegmentTypePostRef)
+}
+
 // IsAtAll 检查消息是否@了所有人
 func IsAtAll(segments model.MessageSegments) bool {
 	return slices.ContainsFunc(segments, func(segment model.MessageSegment) bool {