Refactor user account management by replacing User entity with UserAccount, updating UserController and UserService for CRUD operations, and modifying MyBatis mappers accordingly.

src/main/java/com/gameplatform/server/model/User.java

@@ -1,51 +0,0 @@
-package com.gameplatform.server.model;
-
-import jakarta.validation.constraints.Email;
-import jakarta.validation.constraints.NotBlank;
-
-import java.time.LocalDateTime;
-
-public class User {
-    private Long id;
-
-    @NotBlank
-    private String username;
-
-    @Email
-    private String email;
-
-    private LocalDateTime createdAt;
-
-    public Long getId() {
-        return id;
-    }
-
-    public void setId(Long id) {
-        this.id = id;
-    }
-
-    public String getUsername() {
-        return username;
-    }
-
-    public void setUsername(String username) {
-        this.username = username;
-    }
-
-    public String getEmail() {
-        return email;
-    }
-
-    public void setEmail(String email) {
-        this.email = email;
-    }
-
-    public LocalDateTime getCreatedAt() {
-        return createdAt;
-    }
-
-    public void setCreatedAt(LocalDateTime createdAt) {
-        this.createdAt = createdAt;
-    }
-}
-