feat(user-apps): appearance settings (dark mode + reduced motion), product morph, filter sheet

Applies to both user-app and user-app-v2. Logic and structure are shared;
each app keeps its own look.

Appearance settings
- New "تنظیمات ظاهری" page (/settings/appearance), opened from the
  dashboard and available without login. It offers a light/dark/system
  theme and a "fast & light" motion switch.
- appearanceStore saves the choice to localStorage. A small inline boot
  script in index.html applies it before first paint so there is no
  white flash. The "system" option follows OS changes live.
- New ToggleSwitch component.

Dark mode
- Theme LESS tokens now compile to CSS custom properties. Light/dark
  values come from a generated virtual:palette.css (themeConfig/
  appearance.ts, with colors.json + new colors.dark.json).
- New LESS alpha() plugin replaces fade() on theme tokens.
- New semantic tokens: page, onInk, heroSurface, hairlineStrong,
  photoMat, photoStage.
- The dark palette is layered (page < card < panel < border) so
  surfaces separate without shadows.
- Hard-coded colors were replaced by tokens according to their role.
- antd inputs/text get dark overrides; vant uses its own
  .van-theme-dark.
- Light mode looks the same as before.

Reduced motion
- With html.motion-reduced, transitions are capped at 120ms, keyframe
  loops stop, and backdrop blurs and permanent will-change are dropped.
- Spinners and the toast progress bar (which closes the toast) are
  exempt via .keep-motion.
- Carousel autoplay, the v1 Lottie and the product morph honor the
  setting.

Product detail
- Opening a product is now a container-transform morph from the tapped
  card (ProductMorph). It replaces the bottom Drawer and uses composited
  transform/opacity only.
- The detail view is seeded with the card's data, so it no longer
  opens blank and jumps.

Filters and sheets
- Filters are now a full-width bottom sheet. Selections stay a draft
  until applied, so the result list no longer re-renders while
  dragging the slider.
- DropDown collapse animates grid-template-rows instead of a capped
  max-height.
- v2 IslandSheet is restyled to the v2 design language (API unchanged).

Fixes
- filtersStore.reset() shallow-copied shared arrays, so clearing the
  filters never cleared the selected brands.

apps/user-app/src/components/ui/ToastCard.vue

@@ -29,7 +29,7 @@
 
     <span
       v-if="item.duration > 0"
-      class="toast__progress"
+      class="toast__progress keep-motion"
       :style="{ animationDuration: `${item.duration}ms` }"
       @animationend="emit('close')"
     />
@@ -132,14 +132,14 @@ function onUp() {
 
   // Same glass recipe as the bottom nav, so the two read as one system.
   background:
-    radial-gradient(120% 160% at 0% 0%, fade(@canvas, 60%) 0%, fade(@canvas, 0%) 55%),
-    radial-gradient(80% 140% at 100% 100%, fade(@ink, 4%) 0%, fade(@ink, 0%) 60%),
-    linear-gradient(160deg, fade(@canvas, 72%) 0%, fade(@canvas, 50%) 100%);
+    radial-gradient(120% 160% at 0% 0%, alpha(@canvas, 60%) 0%, alpha(@canvas, 0%) 55%),
+    radial-gradient(80% 140% at 100% 100%, alpha(@ink, 4%) 0%, alpha(@ink, 0%) 60%),
+    linear-gradient(160deg, alpha(@canvas, 72%) 0%, alpha(@canvas, 50%) 100%);
   -webkit-backdrop-filter: blur(24px) saturate(200%) brightness(1.05);
   backdrop-filter: blur(24px) saturate(200%) brightness(1.05);
   box-shadow:
-    inset 0 1px 1px fade(@canvas, 90%),
-    inset 0 0 0 0.5px fade(@canvas, 40%),
+    inset 0 1px 1px alpha(@canvas, 90%),
+    inset 0 0 0 0.5px alpha(@canvas, 40%),
     0 18px 40px -16px rgba(20, 22, 26, 0.35),
     0 1px 3px rgba(20, 22, 26, 0.06);
 
@@ -152,10 +152,10 @@ function onUp() {
     border-radius: inherit;
     background: linear-gradient(
       145deg,
-      fade(@canvas, 100%) 0%,
-      fade(@canvas, 30%) 40%,
-      fade(@canvas, 10%) 70%,
-      fade(@canvas, 70%) 100%
+      alpha(@canvas, 100%) 0%,
+      alpha(@canvas, 30%) 40%,
+      alpha(@canvas, 10%) 70%,
+      alpha(@canvas, 70%) 100%
     );
     -webkit-mask:
       linear-gradient(#000 0 0) content-box,
@@ -189,7 +189,7 @@ function onUp() {
 
 @supports not ((backdrop-filter: blur(1px)) or (-webkit-backdrop-filter: blur(1px))) {
   .toast {
-    background: fade(@canvas, 96%);
+    background: alpha(@canvas, 96%);
   }
 }