feat(i18n): complete Japanese localization and eliminate UI hardcoded strings (#753)

Completes the Japanese catalog (all commands, panels, dialogs and preferences) and routes the remaining hard-coded UI labels through the translation lookup. English stays the default.

crates/ui-egui/src/sketch_tools.rs

@@ -1221,7 +1221,7 @@ pub fn show(app: &mut SolveApp, ui: &egui::Ui, painter: &egui::Painter, proj: &P
 fn text_entry(app: &mut SolveApp, ctx: &egui::Context) {
     let Some((at, mut text)) = TEXT.with(|t| t.borrow_mut().take()) else { return };
     let mut done = None;
-    crate::frame::window(ctx, "Text", crate::frame::Width::Normal)
+    crate::frame::window(ctx, crate::i18n::tr_label("Text"), crate::frame::Width::Normal)
         .collapsible(false)
         .resizable(false)
         .anchor(egui::Align2::CENTER_CENTER, egui::vec2(0.0, 0.0))