完善角色与消息权限：收紧板管内容处置，彻底删除仅站长，并统一管理删帖/评弹窗。

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

backend/handler/admin_user.go

@@ -73,6 +73,27 @@ func (h *Handlers) AdminUpdateUserRole(c *gin.Context) {
 	c.JSON(http.StatusOK, gin.H{"user": user})
 }
 
+// AdminSetUserMessages 站长授予/撤销站点消息管理
+func (h *Handlers) AdminSetUserMessages(c *gin.Context) {
+	id, ok := parseAdminUserID(c)
+	if !ok {
+		return
+	}
+	var body struct {
+		CanManageMessages bool `json:"can_manage_messages"`
+	}
+	if err := c.ShouldBindJSON(&body); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "请求参数无效"})
+		return
+	}
+	user, err := h.AdminUser.SetCanManageMessages(middleware.CurrentActor(c), id, body.CanManageMessages)
+	if err != nil {
+		respondAdminUserError(c, err)
+		return
+	}
+	c.JSON(http.StatusOK, gin.H{"user": user})
+}
+
 // AdminSetUserBan 封禁 / 解封用户
 func (h *Handlers) AdminSetUserBan(c *gin.Context) {
 	id, ok := parseAdminUserID(c)