ui: rename Ui class to UrwidUserInterface

pqcli/ui/urwid/custom_line_box.py

@@ -0,0 +1,18 @@
+import typing as T
+
+import urwid
+
+
+class CustomLineBox(urwid.AttrMap):
+    def __init__(
+        self, widget: urwid.Widget, *args: T.Any, **kwargs: T.Any
+    ) -> None:
+        super().__init__(
+            urwid.LineBox(
+                urwid.AttrMap(widget, "linebox-content", "linebox-content"),
+                *args,
+                **kwargs,
+            ),
+            "linebox",
+            "linebox-focus",
+        )