feat: 添加 SignalR 基础设施（Hub + Redis Backplane + JWT 认证）

- 添加 Microsoft.AspNetCore.SignalR.StackExchangeRedis NuGet 包
- 新建 OrderBoardHub（连接/断开/切换门店 Group）
- 新建 SignalRJwtEvents（WebSocket query string JWT 提取）
- Program.cs 注册 SignalR + Redis Backplane + MapHub
- JwtAuthenticationExtensions 添加 OnMessageReceived 事件
- CORS 修复 AllowAnyOrigin 与 AllowCredentials 互斥问题

src/Infrastructure/TakeoutSaaS.Infrastructure/Identity/Extensions/JwtAuthenticationExtensions.cs

@@ -47,6 +47,24 @@ public static class JwtAuthenticationExtensions
                     NameClaimType = ClaimTypes.NameIdentifier,
                     RoleClaimType = ClaimTypes.Role
                 };
+
+                // SignalR WebSocket 通过 query string 传递 JWT
+                options.Events = new JwtBearerEvents
+                {
+                    OnMessageReceived = context =>
+                    {
+                        if (context.Request.Path.StartsWithSegments("/hubs"))
+                        {
+                            var token = context.Request.Query["access_token"];
+                            if (!string.IsNullOrEmpty(token))
+                            {
+                                context.Token = token;
+                            }
+                        }
+
+                        return Task.CompletedTask;
+                    }
+                };
             });
 
         return services;