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-v2/themeConfig/themeConfig.ts

@@ -3,6 +3,7 @@
 // out of scope for a presentation-only port and superseded by this app's own
 // src/api/client.ts, which already talks to the new NestJS API.)
 import data from './colors.json'
+import { themeLessVarOverrides } from './appearance'
 
 const colors = data
 const curve = {
@@ -40,4 +41,13 @@ const vars = {
   'transition-duration': '.5s',
   'transition-delay': '.5s',
 }
-export const $themeLessVars = Object.assign(vars, colors)
+// Theme tokens (see appearance.ts) are overridden last, so @canvas, @ink, …
+// compile to var(--c-…) and switch with the theme at runtime. The antd keys
+// above were already resolved to hex from `colors`, so antd still gets real
+// colours for its colour functions; only its surface backgrounds follow the
+// theme.
+export const $themeLessVars = Object.assign(vars, colors, themeLessVarOverrides, {
+  'component-background': 'var(--c-canvas)',
+  'body-background': 'var(--c-page)',
+  'popover-background': 'var(--c-canvas)',
+})