Require msgcat before initialising ttkbootstrap

app/gui/theme.py

@@ -30,6 +30,11 @@ class ThemeMixin:
     def init_theme(self) -> None:
         """Initialise ttk style handling and apply the detected theme."""
         if HAS_TTKBOOTSTRAP:
+            try:
+                # Ensure msgcat package is available before ttkbootstrap initialises translations
+                self.root.tk.call("package", "require", "msgcat")  # type: ignore[attr-defined]
+            except Exception:
+                pass
             self.style = tb.Style()
             self.using_tb = True
         else: