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/auth.go

@@ -301,14 +301,15 @@ func meUserBody(user *model.User, boardIDs []uint) gin.H {
 		boardIDs = []uint{}
 	}
 	return gin.H{
-		"id":        user.ID,
-		"username":  user.Username,
-		"nickname":  user.Nickname,
-		"avatar":    user.Avatar,
-		"signature": user.Signature,
-		"email":     user.Email,
-		"role":      user.Role,
-		"board_ids": boardIDs,
+		"id":                  user.ID,
+		"username":            user.Username,
+		"nickname":            user.Nickname,
+		"avatar":              user.Avatar,
+		"signature":           user.Signature,
+		"email":               user.Email,
+		"role":                user.Role,
+		"board_ids":           boardIDs,
+		"can_manage_messages": user.CanManageMessages,
 	}
 }
 
@@ -346,8 +347,15 @@ func (h *Handlers) Me(c *gin.Context) {
 	if user.Role == model.RoleBoardAdmin {
 		boardIDs, _ = h.Auth.GetUserBoardIDs(claims.ID)
 	}
+	body := meUserBody(user, boardIDs)
+	// 群管理员数量：非站长/超管用于后台消息入口判定
+	if h.Chat != nil && user.Role != model.RoleOwner && user.Role != model.RoleSuperAdmin {
+		if n, err := h.Chat.CountAdminRooms(user.ID); err == nil {
+			body["chat_admin_room_count"] = n
+		}
+	}
 	c.JSON(http.StatusOK, gin.H{
-		"user":              meUserBody(user, boardIDs),
+		"user":              body,
 		"unread_count":      unread,
 		"chat_unread_count": chatUnread,
 	})