T1.1: Create src/domain; move Job/RunRecord/Config/JobsFile/StartInTrayArgument

Extracts the five domain types out of src/core/model.go into a new
src/domain package (job.go, record.go, config.go). The unexported
nextDue field is promoted to NextDue so it is accessible from core.
All references across src/core, src/gui, and cmd/gosentry are updated
to use domain.TypeName. src/core/model.go is reduced to a bare package
declaration. Windows and Linux cross-compilation both pass; all tests
remain green.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/core/autostart_windows.go

@@ -6,6 +6,8 @@ import (
 	"os/exec"
 	"path/filepath"
 	"strings"
+
+	"gitea.mixdep.ru/mix/gosentry/src/domain"
 )
 
 const autostartName = "GoSentry"
@@ -69,7 +71,7 @@ func AutostartStatus(expectedEnabled bool, executablePath string) (bool, string)
 	if !sameWindowsPath(actual, executablePath) {
 		return false, "Autostart shortcut points to another executable"
 	}
-	if strings.TrimSpace(arguments) != StartInTrayArgument {
+	if strings.TrimSpace(arguments) != domain.StartInTrayArgument {
 		return false, "Autostart shortcut does not start in tray"
 	}
 	return true, "Autostart is configured"
@@ -101,7 +103,7 @@ func createStartupShortcut(shortcutPath string, executablePath string, iconPath
 	command.Env = append(os.Environ(),
 		"GOSENTRY_SHORTCUT_PATH="+shortcutPath,
 		"GOSENTRY_TARGET_PATH="+executablePath,
-		"GOSENTRY_ARGUMENTS="+StartInTrayArgument,
+		"GOSENTRY_ARGUMENTS="+domain.StartInTrayArgument,
 		"GOSENTRY_WORKING_DIRECTORY="+workingDirectory,
 		"GOSENTRY_ICON_PATH="+iconPath,
 	)