refactor(settings): 简化流超时配置，移除冗余字段

- 移除 TimeoutSeconds 字段，超时判定由网关配置控制
- 默认禁用流超时处理功能

backend/internal/service/setting_service.go

@@ -696,15 +696,6 @@ func (s *SettingService) GetStreamTimeoutSettings(ctx context.Context) (*StreamT
 	}
 
 	// 验证并修正配置值
-	if settings.TimeoutSeconds < 0 {
-		settings.TimeoutSeconds = 0
-	}
-	if settings.TimeoutSeconds > 0 && settings.TimeoutSeconds < 30 {
-		settings.TimeoutSeconds = 30
-	}
-	if settings.TimeoutSeconds > 300 {
-		settings.TimeoutSeconds = 300
-	}
 	if settings.TempUnschedMinutes < 1 {
 		settings.TempUnschedMinutes = 1
 	}
@@ -742,12 +733,6 @@ func (s *SettingService) SetStreamTimeoutSettings(ctx context.Context, settings
 	}
 
 	// 验证配置值
-	if settings.TimeoutSeconds < 0 {
-		return fmt.Errorf("timeout_seconds must be non-negative")
-	}
-	if settings.TimeoutSeconds > 0 && (settings.TimeoutSeconds < 30 || settings.TimeoutSeconds > 300) {
-		return fmt.Errorf("timeout_seconds must be 0 or between 30-300")
-	}
 	if settings.TempUnschedMinutes < 1 || settings.TempUnschedMinutes > 60 {
 		return fmt.Errorf("temp_unsched_minutes must be between 1-60")
 	}

backend/internal/service/settings_view.go

@@ -70,12 +70,10 @@ type PublicSettings struct {
 	Version             string
 }
 
-// StreamTimeoutSettings 流超时处理配置
+// StreamTimeoutSettings 流超时处理配置（仅控制超时后的处理方式，超时判定由网关配置控制）
 type StreamTimeoutSettings struct {
 	// Enabled 是否启用流超时处理
 	Enabled bool `json:"enabled"`
-	// TimeoutSeconds 流数据间隔超时阈值（秒），0表示禁用
-	TimeoutSeconds int `json:"timeout_seconds"`
 	// Action 超时后的处理方式: "temp_unsched" | "error" | "none"
 	Action string `json:"action"`
 	// TempUnschedMinutes 临时不可调度持续时间（分钟）
@@ -96,8 +94,7 @@ const (
 // DefaultStreamTimeoutSettings 返回默认的流超时配置
 func DefaultStreamTimeoutSettings() *StreamTimeoutSettings {
 	return &StreamTimeoutSettings{
-		Enabled:                true,
-		TimeoutSeconds:         60,
+		Enabled:                false,
 		Action:                 StreamTimeoutActionTempUnsched,
 		TempUnschedMinutes:     5,
 		ThresholdCount:         3,