管理后台 server 使用蓝图模式，降低维护成本，降低修改功能时对其他模块的影响

admin/dashboard/blueprints/messages.py

@@ -1,4 +1,4 @@
-from flask import Blueprint, render_template, jsonify, request
+from flask import Blueprint, render_template, jsonify, request, current_app
 from .auth import login_required
 import logging
 import xml.etree.ElementTree as ET
@@ -22,7 +22,7 @@ def message_list_page():
 def get_messages():
     """获取消息列表API"""
     try:
-        server = messages_bp.server
+        server = current_app.dashboard_server
         # 获取查询参数
         group_id = request.args.get('group_id')
         start_date = request.args.get('start_date', datetime.now().strftime('%Y-%m-%d'))
@@ -75,7 +75,7 @@ def get_messages():
 def get_groups():
     """获取群组列表API"""
     try:
-        server = messages_bp.server
+        server = current_app.dashboard_server
         # 获取机器人管理的群组列表
         groups = []
         for group_id in server.contact_manager.get_contacts():