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/run.go

@@ -0,0 +1,60 @@
+package ui
+
+import (
+	"time"
+
+	"gitea.mixdep.ru/mix/gosentry/assets"
+	"gitea.mixdep.ru/mix/gosentry/src/app"
+
+	"fyne.io/fyne/v2"
+	fyneapp "fyne.io/fyne/v2/app"
+)
+
+const appID = "ru.mixdep.gosentry.desktop"
+
+// Run is the application entry point. It owns the process lifecycle — single
+// instance arbitration, Fyne app + window construction, tray wiring, and the
+// startup-timing record — and delegates all view construction to newMainView in
+// mainwindow.go. Keeping lifecycle here and the view there is the run.go /
+// mainwindow.go split introduced in T4.1.
+func Run(startInTray bool) {
+	started := time.Now()
+	instanceListener, primary := acquireSingleInstance(!startInTray)
+	if !primary {
+		return
+	}
+	if instanceListener != nil {
+		defer instanceListener.Close()
+	}
+
+	// A stable app ID lets Fyne persist desktop preferences consistently across
+	// launches and gives tray/window integration a predictable identity.
+	a := fyneapp.NewWithID(appID)
+	a.SetIcon(loadAppIcon())
+
+	w := a.NewWindow("GoSentry " + app.Version)
+	configureSystemTray(a, w)
+	w.Resize(fyne.NewSize(1120, 720))
+	content, recordStartup := newMainView(w)
+	w.SetContent(content)
+	serveSingleInstance(instanceListener, w)
+	if startInTray {
+		// Autostart launches intentionally stay hidden, so "window shown" would be
+		// a misleading metric. Record a separate startup event for the tray path
+		// instead of forcing one timing definition onto two different UX flows.
+		recordStartup(time.Since(started), false)
+		a.Run()
+		return
+	}
+	// Show the window before recording startup time. Measuring earlier, during
+	// widget construction, looked cheaper in History than the user-perceived
+	// startup really was. The current point is less abstract: it ends when the
+	// window has actually been handed to the desktop for display.
+	w.Show()
+	recordStartup(time.Since(started), true)
+	a.Run()
+}
+
+func loadAppIcon() fyne.Resource {
+	return assets.Icon()
+}