feat: relocate remaining dtos

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

@@ -0,0 +1,30 @@
+package com.openisle.dto;
+
+import lombok.Data;
+
+import java.time.LocalDateTime;
+
+/** Detailed user information. */
+@Data
+public class UserDto {
+    private Long id;
+    private String username;
+    private String email;
+    private String avatar;
+    private String role;
+    private String introduction;
+    private long followers;
+    private long following;
+    private LocalDateTime createdAt;
+    private LocalDateTime lastPostTime;
+    private LocalDateTime lastCommentTime;
+    private long totalViews;
+    private long visitedDays;
+    private long readPosts;
+    private long likesSent;
+    private long likesReceived;
+    private boolean subscribed;
+    private int experience;
+    private int currentLevel;
+    private int nextLevelExp;
+}