T4.1: Rename gui->ui, split lifecycle into run.go + mainwindow.go

Carve src/gui/app.go into the new src/ui package:
- run.go: process lifecycle (single instance, app/window, tray, startup
  timing).
- mainwindow.go: view assembly + the app.Service event listener.

Route every widget update driven by Service events through fyne.Do so the
run goroutine (executeRun) no longer mutates Fyne widgets directly. Also
wrap serveSingleInstance's Show/RequestFocus, which runs on the Accept
goroutine. (Resolves refactoring problem #4.)

fyne.Do/DoAndWait only exist in Fyne v2.6+, so upgrade fyne.io/fyne/v2
v2.5.3 -> v2.6.3. Mark the tray Quit item IsQuit so Fyne's
addMissingQuitForMenu reuses it instead of appending a second, localized
Quit now that v2.6 ships Russian translations.

go build / go vet / go test -race all clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/ui/run.go

@@ -0,0 +1,151 @@
+package ui
+
+import (
+	"io"
+	"net"
+	"strings"
+	"time"
+
+	"gitea.mixdep.ru/mix/gosentry/assets"
+	"gitea.mixdep.ru/mix/gosentry/src/app"
+
+	"fyne.io/fyne/v2"
+	fyneapp "fyne.io/fyne/v2/app"
+	fynedesktop "fyne.io/fyne/v2/driver/desktop"
+)
+
+const appID = "ru.mixdep.gosentry.desktop"
+const singleInstanceAddress = "127.0.0.1:37653"
+const singleInstanceShowCommand = "show"
+
+// 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()
+}
+
+func configureSystemTray(a fyne.App, w fyne.Window) {
+	desk, ok := a.(fynedesktop.App)
+	if !ok {
+		// Not every Fyne driver exposes desktop tray features. Returning silently
+		// keeps the same binary usable on platforms or sessions without a tray.
+		return
+	}
+
+	// IsQuit marks this as the tray's quit item. Without it Fyne's
+	// addMissingQuitForMenu appends a second, localized Quit (e.g. "Выход" on a
+	// Russian system) because it only recognizes an existing quit by matching the
+	// localized label — which our literal "Quit" does not. Setting IsQuit makes
+	// Fyne reuse this item instead of adding a duplicate, regardless of locale.
+	quit := fyne.NewMenuItem("Quit", func() {
+		a.Quit()
+	})
+	quit.IsQuit = true
+	menu := fyne.NewMenu("GoSentry",
+		fyne.NewMenuItem("Show", func() {
+			w.Show()
+			w.RequestFocus()
+		}),
+		fyne.NewMenuItemSeparator(),
+		quit,
+	)
+	desk.SetSystemTrayMenu(menu)
+	w.SetCloseIntercept(func() {
+		// Closing hides the window instead of quitting because scheduler tools are
+		// expected to keep working in the background. The explicit Quit tray item
+		// remains the way to stop the process.
+		w.Hide()
+	})
+}
+
+func acquireSingleInstance(showExisting bool) (net.Listener, bool) {
+	listener, err := net.Listen("tcp", singleInstanceAddress)
+	if err == nil {
+		return listener, true
+	}
+
+	connection, dialErr := net.DialTimeout("tcp", singleInstanceAddress, time.Second)
+	if dialErr == nil {
+		// The first instance listens only on localhost and understands one tiny
+		// command: "show". That keeps the implementation dependency-free and easy
+		// to inspect, which matters more here than introducing a named-pipe or
+		// platform-specific IPC abstraction just to focus an existing window.
+		if showExisting {
+			_, _ = io.WriteString(connection, singleInstanceShowCommand)
+		}
+		_ = connection.Close()
+		return nil, false
+	}
+
+	// If the port is unavailable but does not answer as GoSentry, continue
+	// startup instead of making the application impossible to open because of an
+	// unrelated local listener. In the normal duplicate-start case the dial above
+	// succeeds and this process exits after waking the first instance.
+	return nil, true
+}
+
+func serveSingleInstance(listener net.Listener, w fyne.Window) {
+	if listener == nil {
+		return
+	}
+	go func() {
+		for {
+			connection, err := listener.Accept()
+			if err != nil {
+				return
+			}
+			command, _ := io.ReadAll(io.LimitReader(connection, 32))
+			_ = connection.Close()
+			if strings.TrimSpace(string(command)) != singleInstanceShowCommand {
+				continue
+			}
+			// Accept runs on its own goroutine, so focusing the window must be
+			// marshaled onto the main thread like every other widget update.
+			fyne.Do(func() {
+				w.Show()
+				w.RequestFocus()
+			})
+		}
+	}()
+}