Set window icon on Admin Panel (title bar + taskbar)

Embed the blue SyncWarden shield icon in the panel binary and set it
as the window icon via Win32 SendMessage/WM_SETICON on startup.
Uses the syncing (blue) variant as the status-independent panel icon.

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

cmd/panel/main.go

@@ -19,6 +19,10 @@ func main() {
 
 	w.SetTitle("SyncWarden — Admin Panel")
 	w.SetSize(1024, 768, webview.HintNone)
+
+	// Set window icon (title bar + taskbar)
+	setWindowIcon(w.Window())
+
 	w.Navigate(*addr)
 	w.Run()
 }