feat(msg): SSE 实时通知体系 (Phase 1-4 + 7 部分)

后端:
- MessageSseService (emitter 注册表, 25s 心跳, pushNewMessage 仅 log 不抛)
- BizMessageSseController (独立 Controller, 避开 /{msgId} 路径抢匹配)
- BizMessageMapper.countUnread SQL 修复 (跟 limit 解耦, SSE 推真值)
- BizMessageServiceImpl.insert/markRead 成功后 pushNewMessage 触发 SSE
- BizNotifyService.expertAuditResult (#1: 审核结果通知专家本人)
- BizExpertServiceImpl.updateByPrimaryKey 比对旧 audit_status, 真变化才发通知
- PlaceholderConfig (Spring 7 严格 placeholder 兜底, ignoreUnresolvable=true)

前端:
- utils/sseClient.js (@microsoft/fetch-event-source 封装, Bearer 鉴权, 单例连接)
- 全局事件总线 onGlobal: SSE new_message 扇出到业务页面 (切路由不掉)
- AdminLayout 全局订阅 + bell 角标 (el-badge 显示 unreadCount)
- userStore.expertAuditApproved: doctor 审核状态实时跟 DB
- AdminLayout doctor menu 加 requireAuditApproved 过滤 (未通过审核隐藏 3 menu)
- doctor/Home: 待参加会议/待签协议 2 pannel 按 audit 状态显示; load() 仅审核通过才拉数据
- doctor/Home + doctor/Messages: 点列表弹详情 dialog + markMessageRead 真已读
- AdminLayout SSE 触发时: 刷新 unread + 重新拉 audit 状态 (审核通过瞬间可见)

业务规则:
- 专家注册不群发 manager (manager 群体可能 100+, 每条注册发 N 条浪费)
- 通过审核无需重新登录 (SSE 链路实时联动)

ry-vue3/package.json

@@ -9,6 +9,7 @@
   },
   "dependencies": {
     "@element-plus/icons-vue": "^2.3.0",
+    "@microsoft/fetch-event-source": "^2.0.1",
     "@wangeditor/editor": "^5.1.23",
     "@wangeditor/editor-for-vue": "^5.1.12",
     "axios": "^1.6.0",