Refactoring complete: v0.4.0 architectural milestone (#1)

## Summary

Completed Phase 5 refactoring and reached the target architecture.

**Architectural milestone achieved:**
- Service layer owns all state and is the sole writer
- UI is a thin Fyne view, all widget updates marshaled via `fyne.Do`
- Core engines are stateless and injectable
- Domain types are pure (no `yaml:"-"` fields)
- Full module builds and `go vet ./...` clean

## Changes

- Bump version: 0.3.6 → 0.4.0
- Update CHANGELOG with Phase 5 summary
- Add ROADMAP "Refactoring Follow-Ups" section

## Known follow-up work

1. **Linux test build broken** — `runner_test.go` needs `//go:build windows` tag
2. **File-size limits exceeded** — `operations.go` (486 lines), `jobs_view.go` (415 lines)

See ROADMAP.md for details.

---------

Co-authored-by: mixeme <mix.public@ya.ru>
Reviewed-on: #1

src/ui/job_dialog.go

@@ -0,0 +1,90 @@
+package ui
+
+import (
+	"fmt"
+	"strings"
+
+	"gitea.mixdep.ru/mix/gosentry/src/app"
+	"gitea.mixdep.ru/mix/gosentry/src/domain"
+
+	"fyne.io/fyne/v2"
+	"fyne.io/fyne/v2/dialog"
+	"fyne.io/fyne/v2/widget"
+)
+
+// showJobDialog opens a create/edit form for a single job. onSave is called
+// with the populated job only when the user clicks Save and all fields pass
+// validation.
+func showJobDialog(w fyne.Window, title string, current job, onSave func(job)) {
+	name := widget.NewEntry()
+	name.SetPlaceHolder("Nightly backup")
+	name.SetText(current.Name)
+	folderEntry := widget.NewEntry()
+	folderEntry.SetPlaceHolder("Maintenance")
+	folderEntry.SetText(current.Folder)
+	scheduleEntry := widget.NewEntry()
+	scheduleEntry.SetPlaceHolder("@every 1m")
+	scheduleEntry.SetText(current.Schedule)
+	commandEntry := widget.NewEntry()
+	commandEntry.SetPlaceHolder(`C:\Program Files\App\App.exe`)
+	commandEntry.SetText(current.Command)
+	argumentsEntry := widget.NewMultiLineEntry()
+	argumentsEntry.SetPlaceHolder(`D:\Local\Jobs\Auto.ffs_batch`)
+	argumentsEntry.SetText(current.Arguments)
+	successExitCodesEntry := widget.NewEntry()
+	successExitCodesEntry.SetPlaceHolder("0")
+	successExitCodesEntry.SetText(app.DisplaySuccessExitCodes(current.SuccessExitCodes))
+	startOnly := widget.NewCheck("Start only, do not wait for exit", nil)
+	startOnly.SetChecked(current.StartOnly)
+	enabled := widget.NewCheck("Enabled", nil)
+	enabled.SetChecked(current.Enabled)
+
+	form := dialog.NewForm(
+		title,
+		"Save",
+		"Cancel",
+		[]*widget.FormItem{
+			widget.NewFormItem("Name", name),
+			widget.NewFormItem("Folder", folderEntry),
+			widget.NewFormItem("Schedule", scheduleEntry),
+			widget.NewFormItem("Command", commandEntry),
+			widget.NewFormItem("Arguments", argumentsEntry),
+			widget.NewFormItem("Success exit codes", successExitCodesEntry),
+			widget.NewFormItem("", startOnly),
+			widget.NewFormItem("", enabled),
+		},
+		func(saved bool) {
+			if !saved {
+				return
+			}
+			if strings.TrimSpace(name.Text) == "" || strings.TrimSpace(scheduleEntry.Text) == "" || strings.TrimSpace(commandEntry.Text) == "" {
+				// These three fields are the minimum executable job definition.
+				// Folder is optional because ungrouped jobs are a supported workflow.
+				dialog.ShowError(fmt.Errorf("name, schedule, and command are required"), w)
+				return
+			}
+			if err := domain.Validate(strings.TrimSpace(scheduleEntry.Text)); err != nil {
+				dialog.ShowError(fmt.Errorf("invalid schedule: %w", err), w)
+				return
+			}
+			current.Name = strings.TrimSpace(name.Text)
+			current.Folder = strings.TrimSpace(folderEntry.Text)
+			current.Schedule = strings.TrimSpace(scheduleEntry.Text)
+			current.Command = strings.TrimSpace(commandEntry.Text)
+			current.Arguments = strings.TrimSpace(argumentsEntry.Text)
+			current.SuccessExitCodes = strings.TrimSpace(successExitCodesEntry.Text)
+			if current.SuccessExitCodes == "" {
+				current.SuccessExitCodes = "0"
+			}
+			current.StartOnly = startOnly.Checked
+			current.Enabled = enabled.Checked
+			// The dialog only edits durable configuration. Runtime status is
+			// initialized (new jobs) or updated (edits) by the caller against the
+			// runtime map, keyed by job ID.
+			onSave(current)
+		},
+		w,
+	)
+	form.Resize(fyne.NewSize(640, 460))
+	form.Show()
+}