feat(server): online session history with configurable stats window (#1243)

Add persisted online sessions, configurable retention and online history statistics with lifecycle, recovery, timezone and concurrency regression coverage.

Co-authored-by: naiba/CloudCode <hi+cloudcode@nai.ba>

cmd/dashboard/controller/setting.go

@@ -2,6 +2,7 @@ package controller
 
 import (
 	"errors"
+	"fmt"
 	"log"
 	"strings"
 
@@ -29,7 +30,7 @@ func listConfig(c *gin.Context) (*model.SettingResponse, error) {
 		isAdmin = user.Role.IsAdmin()
 	}
 
-	config := *singleton.Conf
+	config := singleton.Conf.SettingsSnapshot()
 	config.Language = strings.ReplaceAll(config.Language, "_", "-")
 
 	conf := model.SettingResponse{
@@ -92,6 +93,12 @@ func updateConfig(c *gin.Context) (any, error) {
 	if !userTemplateValid {
 		return nil, errors.New("invalid user template")
 	}
+	// 全部输入校验必须先于任何对 singleton.Conf 的写入：任一字段非法都应
+	// 整体拒绝，避免"请求以错误收场、先处理的字段却已生效"的半提交状态
+	if sf.OnlineStatsDays != nil &&
+		(*sf.OnlineStatsDays < model.MinOnlineStatsDays || *sf.OnlineStatsDays > model.MaxOnlineStatsDays) {
+		return nil, fmt.Errorf("online_stats_days must be between %d and %d", model.MinOnlineStatsDays, model.MaxOnlineStatsDays)
+	}
 
 	singleton.Conf.Language = strings.ReplaceAll(sf.Language, "-", "_")
 
@@ -114,18 +121,23 @@ func updateConfig(c *gin.Context) (any, error) {
 	singleton.Conf.AgentRealIPHeader = sf.AgentRealIPHeader
 	singleton.Conf.AgentTLS = sf.AgentTLS
 	singleton.Conf.UserTemplate = sf.UserTemplate
-	mcpWasEnabled := singleton.Conf.MCPEnabled()
-	mcpNext := resolveSettingEnableMCP(sf.EnableMCP, mcpWasEnabled)
 
-	if err := applyEnableMCPTransition(
-		mcpWasEnabled, mcpNext,
-		singleton.Conf.SetMCPEnabled,
-		singleton.Conf.Save,
-		fireMCPKillSwitch,
-	); err != nil {
+	if err := singleton.Conf.CommitOnlineHistoryRetention(sf.OnlineStatsDays, func() error {
+		mcpWasEnabled := singleton.Conf.MCPEnabled()
+		mcpNext := resolveSettingEnableMCP(sf.EnableMCP, mcpWasEnabled)
+		return applyEnableMCPTransition(
+			mcpWasEnabled, mcpNext,
+			singleton.Conf.SetMCPEnabled,
+			singleton.Conf.Save,
+			fireMCPKillSwitch,
+		)
+	}); err != nil {
 		return nil, newGormError("%v", err)
 	}
 
+	// applyEnableMCPTransition already persisted every setting, even when MCP
+	// is unchanged. A second save could fail after irreversible cleanup.
+
 	singleton.OnUpdateLang(singleton.Conf.Language)
 	return nil, nil
 }