feat(auth): 实现用户会话数限制功能

添加用户会话数限制功能，当超过最大会话数时自动移除最旧的会话
- 在config中添加UserSessionsKeyPrefix常量
- 在JwtAuth配置中新增MaxSessionsPerUser字段
- 在ServiceContext中实现EnforceUserSessionLimit方法
- 在所有登录逻辑中调用会话限制检查

internal/config/cacheKey.go

@@ -42,6 +42,9 @@ const SessionIdKey = "auth:session_id"
 // DeviceCacheKeyKey cache session key
 const DeviceCacheKeyKey = "auth:device_identifier"
 
+// UserSessionsKeyPrefix per-user sessions zset key prefix
+const UserSessionsKeyPrefix = "auth:user_sessions:"
+
 // GlobalConfigKey Global Config Key
 const GlobalConfigKey = "system:global_config"
 

internal/config/config.go

@@ -42,8 +42,9 @@ type RedisConfig struct {
 }
 
 type JwtAuth struct {
-	AccessSecret string `yaml:"AccessSecret"`
-	AccessExpire int64  `yaml:"AccessExpire" default:"604800"`
+	AccessSecret       string `yaml:"AccessSecret"`
+	AccessExpire       int64  `yaml:"AccessExpire" default:"604800"`
+	MaxSessionsPerUser int64  `yaml:"MaxSessionsPerUser" default:"3"`
 }
 
 type Verify struct {