[client] UI refactor (#6069)

Refactor UI

---------

Co-authored-by: Eduard Gert <kontakt@eduardgert.de>
Co-authored-by: braginini <bangvalo@gmail.com>
Co-authored-by: Pascal Fischer <32096965+pascal-fischer@users.noreply.github.com>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: riccardom <riccardomanfrin@gmail.com>

client/ui/tray_label_windows.go

@@ -0,0 +1,11 @@
+//go:build windows
+
+package main
+
+import "strings"
+
+// menuLabel doubles ampersands so Win32 draws a literal "&" instead of
+// consuming it as the menu mnemonic prefix (Wails passes the label unescaped).
+func menuLabel(s string) string {
+	return strings.ReplaceAll(s, "&", "&&")
+}