fix: 空评论列表 500，并完善撤回审计与角色说明

空切片 JSON 统一为数组；撤回保留正文供站长阅读，成员侧居中提示与重新编辑；头像支持拖放；角色弹窗补全职责说明并汇入封禁。

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/handler/user.go

@@ -104,6 +104,9 @@ func (h *Handlers) UserProfile(c *gin.Context) {
 	if user.Role == model.RoleBoardAdmin {
 		boardIDs, _ = h.Auth.GetUserBoardIDs(user.ID)
 	}
+	if boardIDs == nil {
+		boardIDs = []uint{}
+	}
 
 	c.JSON(http.StatusOK, gin.H{
 		"user": gin.H{
@@ -122,7 +125,7 @@ func (h *Handlers) UserProfile(c *gin.Context) {
 			"points":        pointsTotal,
 			"streak":        streak,
 		},
-		"posts":       posts,
+		"posts":       nonNilSlice(posts),
 		"posts_total": postsTotal,
 		"page":        page,
 		"size":        size,
@@ -152,7 +155,7 @@ func (h *Handlers) UserComments(c *gin.Context) {
 	}
 
 	c.JSON(http.StatusOK, gin.H{
-		"comments": comments,
+		"comments": nonNilSlice(comments),
 		"total":    total,
 		"page":     page,
 		"size":     size,