fix(logger): prevent nil-deref panic in migrate/setting CLI paths

The package-level logger is nil until InitLogger runs, which only happens in runWebServer. The migrate and setting subcommands log without initializing it; PR #5520 added a logger.Info on a success path in MigrationRestoreVisionFlow, so 'x-ui migrate' segfaults on installs with a VLESS inbound needing Vision-flow restoration.

Initialize logger to a usable default at package load so no code path can nil-deref it, and set up the dual backend in migrateDb so migration steps are logged like runWebServer.

Fixes #5581

main.go

@@ -484,6 +484,7 @@ func GetApiToken(getApiToken bool) {
 func migrateDb() {
 	inboundService := service.InboundService{}
 
+	logger.InitLogger(logging.INFO)
 	err := database.InitDB(config.GetDBPath())
 	if err != nil {
 		log.Fatal(err)