[client/uiwails] Windows cross-build support and notification actions

- Add build/windows/Taskfile.yml to cross-compile from Linux with
  mingw-w64 (CC=x86_64-w64-mingw32-gcc, CGO_ENABLED=1, -H=windowsgui).
- Rename xembed_tray.{c,h} to xembed_tray_linux.{c,h} so the Go
  toolchain only compiles these X11/GTK sources on Linux.
- Add sendShowWindowSignal on Windows: opens the named Global event
  and calls SetEvent so the already-running instance shows its window.
- Register a notification category with Open/Dismiss action buttons
  and wire a response handler. Do this inside the ApplicationStarted
  hook so it runs after the notifications service's Startup has
  initialized appName/appGUID on Windows; otherwise the category is
  saved under an empty registry path and SendNotificationWithActions
  silently falls back to a plain toast with no buttons.
- Bump github.com/wailsapp/wails/v3 to v3.0.0-alpha.78.

client/uiwails/Taskfile.yml

@@ -4,6 +4,7 @@ includes:
   common: ./build/Taskfile.yml
   linux: ./build/linux/Taskfile.yml
   darwin: ./build/darwin/Taskfile.yml
+  windows: ./build/windows/Taskfile.yml
 
 vars:
   APP_NAME: "netbird-ui"

client/uiwails/build/windows/Taskfile.yml

@@ -0,0 +1,41 @@
+version: '3'
+
+includes:
+  common: ../Taskfile.yml
+
+tasks:
+  build:
+    summary: Cross-compiles the application for Windows from Linux using mingw-w64
+    cmds:
+      - task: build:cross
+        vars:
+          DEV: '{{.DEV}}'
+          OUTPUT: '{{.OUTPUT}}'
+
+  build:cross:
+    summary: Cross-compiles for Windows with mingw-w64
+    internal: true
+    deps:
+      - task: common:build:frontend
+        vars:
+          DEV:
+            ref: .DEV
+    preconditions:
+      - sh: command -v {{.CC}}
+        msg: "{{.CC}} not found. Install with: sudo apt-get install gcc-mingw-w64-x86-64"
+    cmds:
+      - go build {{.BUILD_FLAGS}} -o {{.OUTPUT}}
+    vars:
+      BUILD_FLAGS: '{{if eq .DEV "true"}}-buildvcs=false -gcflags=all="-l" -ldflags="-H=windowsgui"{{else}}-tags production -trimpath -buildvcs=false -ldflags="-w -s -H=windowsgui"{{end}}'
+      DEFAULT_OUTPUT: '{{.BIN_DIR}}/{{.APP_NAME}}.exe'
+      OUTPUT: '{{ .OUTPUT | default .DEFAULT_OUTPUT }}'
+      CC: '{{.CC | default "x86_64-w64-mingw32-gcc"}}'
+    env:
+      GOOS: windows
+      GOARCH: amd64
+      CGO_ENABLED: 1
+      CC: '{{.CC}}'
+
+  run:
+    cmds:
+      - '{{.BIN_DIR}}/{{.APP_NAME}}.exe'

client/uiwails/main.go

@@ -124,13 +124,48 @@ func main() {
 	evtManager := event.NewManager(*daemonAddr, notify)
 	go evtManager.Start(ctx)
 
-	// TEST: fire a desktop notification shortly after startup so we can
-	// verify that the notification pipeline works end-to-end.
-	go func() {
-		time.Sleep(3 * time.Second)
-		log.Infof("--- trigger notification ---")
-		notify("NetBird Test", "If you see this, notifications are working!")
-	}()
+	// Response handler can be wired early — it's just a callback registration.
+	const testCategoryID = "netbird-test-actions"
+	notifSvc.OnNotificationResponse(func(result notifications.NotificationResult) {
+		if result.Error != nil {
+			log.Warnf("notification response error: %v", result.Error)
+			return
+		}
+		log.Infof("notification action: id=%q category=%q", result.Response.ActionIdentifier, result.Response.CategoryID)
+		if result.Response.ActionIdentifier == "open" {
+			window.Show()
+		}
+	})
+
+	// Category registration and the test notification must happen AFTER the
+	// notifications service has run its Startup (which initializes appName,
+	// appGUID, and the COM activator on Windows). ApplicationStarted fires
+	// after all services are started.
+	app.Event.OnApplicationEvent(events.Common.ApplicationStarted, func(*application.ApplicationEvent) {
+		if err := notifSvc.RegisterNotificationCategory(notifications.NotificationCategory{
+			ID: testCategoryID,
+			Actions: []notifications.NotificationAction{
+				{ID: "open", Title: "Open NetBird"},
+				{ID: "dismiss", Title: "Dismiss"},
+			},
+		}); err != nil {
+			log.Warnf("register notification category: %v", err)
+			return
+		}
+
+		go func() {
+			time.Sleep(3 * time.Second)
+			log.Infof("--- trigger notification ---")
+			if err := notifSvc.SendNotificationWithActions(notifications.NotificationOptions{
+				ID:         "netbird-test",
+				Title:      "NetBird Test (with buttons)",
+				Body:       "ACTIONS TEST — you should see Open/Dismiss buttons below this text.",
+				CategoryID: testCategoryID,
+			}); err != nil {
+				log.Warnf("send notification with actions: %v", err)
+			}
+		}()
+	})
 
 	if err := app.Run(); err != nil {
 		log.Fatalf("app run: %v", err)

client/uiwails/signal_windows.go

@@ -49,6 +49,23 @@ func setupSignalHandler(ctx context.Context, window *application.WebviewWindow)
 	go waitForWindowsEvent(ctx, eventHandle, window)
 }
 
+// sendShowWindowSignal signals the already-running instance (identified by pid,
+// unused on Windows since the event is named globally) to show its window.
+func sendShowWindowSignal(_ int32) error {
+	eventNamePtr, err := windows.UTF16PtrFromString(fancyUITriggerEventName)
+	if err != nil {
+		return err
+	}
+
+	handle, err := windows.OpenEvent(desiredAccesses, false, eventNamePtr)
+	if err != nil {
+		return err
+	}
+	defer windows.CloseHandle(handle)
+
+	return windows.SetEvent(handle)
+}
+
 func waitForWindowsEvent(ctx context.Context, eventHandle windows.Handle, window *application.WebviewWindow) {
 	defer func() {
 		if err := windows.CloseHandle(eventHandle); err != nil {

client/uiwails/xembed_host_linux.go

@@ -5,7 +5,7 @@ package main
 /*
 #cgo pkg-config: x11 gtk+-3.0
 #cgo LDFLAGS: -lX11
-#include "xembed_tray.h"
+#include "xembed_tray_linux.h"
 #include <X11/Xlib.h>
 #include <stdlib.h>
 */

client/uiwails/xembed_tray_linux.c

@@ -1,4 +1,4 @@
-#include "xembed_tray.h"
+#include "xembed_tray_linux.h"
 
 #include <X11/Xatom.h>
 #include <X11/Xutil.h>