修复问题#927,#860

1.优化评论请求，将两个请求合并为一个
2.修改个人主页按钮的主次

backend/src/main/java/com/openisle/dto/TimelineItemDto.java

@@ -0,0 +1,20 @@
+package com.openisle.dto;
+
+import lombok.*;
+
+import java.time.LocalDateTime;
+
+/**
+ * comment and change_log Dto
+ */
+@Getter
+@Setter
+@AllArgsConstructor
+@NoArgsConstructor
+public class TimelineItemDto<T> {
+
+    private Long id;
+    private String kind; // "comment" | "log"
+    private LocalDateTime createdAt;
+    private T payload; // 泛型，具体类型由外部决定
+}