refactor(ui): replace modal dialogs with toast/sheet components

Remove DialogVant/NotifyVant and add Toast and Sheet components with
useToast, useReveal, and usePageTransition composables. Rework
Navigation, RegisterView, and styles across both apps; rebuild dist assets.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/user-app/src/main.ts

@@ -33,11 +33,14 @@ setUnauthorizedHandler(() => {
     void router.push({ name: 'login' });
   }
 });
-// Ported from legacy main.ts:32-46 — Vector.svg is both the while-loading and
-// the on-error placeholder, so a missing/failed image paints the brand mark
-// instead of collapsing the layout.
+// Ported from legacy main.ts:32-46, with one change: the brand mark is now only
+// the on-error placeholder. As the while-loading placeholder it painted the
+// logo into every card first and then swapped it for the real photo a moment
+// later — a visible jump on every image. While loading, the library's own
+// transparent pixel is used instead, the image is held at opacity 0 and fades
+// in once loaded (see `img[lazy]` in style.less); the card's own background
+// stands in until then.
 app.use(VueLazyLoad, {
-  loading: Vector,
   error: Vector,
 });
 app.component('container', Container);