wgui: basic i18n support, refactoring: use LayoutState, translation framework (LLM-based generator)

wlx-overlay-s/src/assets/gui/bar.xml

@@ -20,9 +20,9 @@
         <TopButton id="delete" src="bar/delete.svg" />
       </rectangle>
       <rectangle padding="8" gap="8" round="100%" color="~bg_color_active" justify_content="center" align_items="center">
-        <label size="18" text="Opacity" color="~text_color" />
+        <label size="18" translation="BAR.OPACITY" color="~text_color" />
         <slider width="150" height="24" min_value="0" max_value="100" value="100" />
-        <label size="18" text="Additive:" color="~text_color" />
+        <label size="18" translation="BAR.ADDITIVE" color="~text_color" />
         <sprite color="~device_color" width="20" height="20" src="bar/checkbox-checked.svg" />
       </rectangle>
     </div>

wlx-overlay-s/src/assets/lang/en.json

@@ -0,0 +1 @@
+{}