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/composables/useReveal.ts

@@ -0,0 +1,43 @@
+import { nextTick, ref } from 'vue'
+
+/**
+ * First-paint entrance shared by the tab screens (Home, Dashboard, Cart):
+ * once a screen's first data load lands, its sections rise and fade in one
+ * after another. The styles are the global `.reveal` / `.is-revealed` pair in
+ * assets/styles/style.less.
+ *
+ * MasterLayout renders its routes without keep-alive, so a screen remounts on
+ * every return to its tab. Which screens have already played is kept here in
+ * module scope, so the entrance is a first-run flourish that resets only on a
+ * full reload — replaying it on each tab switch would fight the page
+ * transition rather than add to it. (A `let` at the top of <script setup>
+ * would not do this: that code runs once per mount.)
+ */
+const played = new Set<string>()
+
+export function useReveal(key: string, stepMs = 70) {
+  const revealed = ref(played.has(key))
+
+  // Each item starts a beat after the one before it. Kept small, so the whole
+  // sequence finishes well under a second and reads as the page arriving.
+  function revealDelay(i: number) {
+    return { '--reveal-delay': `${i * stepMs}ms` }
+  }
+
+  // Call once the first load has populated the DOM. Waits for the new nodes
+  // to be mounted, then for one painted frame in their "before" state — with
+  // a single frame the browser can resolve both states in the same style pass
+  // and there is nothing to animate.
+  async function reveal() {
+    if (revealed.value) return
+    await nextTick()
+    requestAnimationFrame(() =>
+      requestAnimationFrame(() => {
+        revealed.value = true
+        played.add(key)
+      }),
+    )
+  }
+
+  return { revealed, revealDelay, reveal }
+}