feat: 补充应急就医对话消息原型并更新文档截图

为操作人员和专业人员补齐对话消息入口与页面，统一应急链路顶部导航并修复通讯录重复添加问题。同时更新应急模块PRD、截图资源与相关原型细节，清理本地截图辅助脚本。

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

index.html

@@ -288,10 +288,12 @@ const SITE_MAP = [
       { file:'work-order.html', label:'应急工单' },
       { file:'call-record.html', label:'通话记录' },
       { file:'duty-group.html', label:'值班小组' },
-      { file:'serious-illness.html', label:'大病就医' }
+      { file:'serious-illness.html', label:'大病就医' },
+      { file:'chat-message.html', label:'对话消息' }
     ]},
     { name:'应急就医(专业人员)', dir:'web-admin/emergency-dispatch/professional', entry:'professional.html', prd:'web-admin/emergency-dispatch/professional/doc/PRD.md', pages:[
-      { file:'professional.html', label:'正在应急' }
+      { file:'professional.html', label:'正在应急' },
+      { file:'chat-message.html', label:'对话消息' }
     ]},
     { name:'一线医疗', dir:'web-admin/frontline-medical', pages:[] }
   ]},