fix(presence-service): JWT guard 用 sub 兼容旧 token 的 userId/accountSequence

旧 token 只有 sub 字段，新 token 有 userId/accountSequence。
用 payload.userId ?? payload.sub 兼容两种格式，
确保旧 token 心跳能正确写入在线状态。

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

backend/services/presence-service/src/shared/guards/jwt-auth.guard.ts

@@ -26,8 +26,8 @@ export class JwtAuthGuard implements CanActivate {
       // 兼容旧 token（无 type 字段）和新 token（type: 'access'）
       if (payload.type && payload.type !== 'access') throw new UnauthorizedException('无效的令牌类型');
       request.user = {
-        userId: payload.userId,
-        accountSequence: payload.accountSequence,
+        userId: payload.userId ?? payload.sub,
+        accountSequence: payload.accountSequence ?? payload.sub,
         deviceId: payload.deviceId,
       };
     } catch {