user-app: redesigned home screen and product detail

Design language introduced here and reused across both screens:
  - LESS colour tokens (@ink/@inkSoft/@inkMuted/@inkFaint, @wine/@wineSoft,
    @canvas/@canvasSoft, @hairline/@hairlineSoft) added to
    themeConfig/colors.json and injected globally via vite's modifyVars, so
    scoped <style lang="less"> blocks resolve them with no import
  - BEM-ish scoped class names, hairline-bordered cards at 14-18px radii,
    ink surfaces with a wine accent, dashed-border empty states
  - components/home/: SectionHead, ShowcaseCard, ShowcaseSlider, CategoryRail,
    RateStrip, AccountStrip

Data honesty is deliberate throughout: no rial price is printed for a piece,
because a finished item's price is the live gold rate x weight plus wage,
computed at order time and never stored on the product. Only genuinely
present fields are shown (weight, making-charge percent, stock, category,
brand). Categories and the hero are derived from the real catalogue, so an
empty catalogue renders an empty state rather than placeholder tiles.

Also fixes a real bug in the product detail view: it ran, at module scope,
history.pushState + window.onpopstate = () => history.go(1). Because the
drawer mounts its slot eagerly, that fired for every product card on the
home screen and permanently hijacked the back button for the session.

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

apps/user-app/src/components/home/SectionHead.vue

@@ -0,0 +1,59 @@
+<!-- Section heading with an optional "see all" affordance. -->
+<template>
+  <header class="sec">
+    <div class="sec__text">
+      <h2 class="sec__title">{{ title }}</h2>
+      <p v-if="subtitle" class="sec__sub">{{ subtitle }}</p>
+    </div>
+    <button v-if="actionLabel" type="button" class="sec__action" @click="emit('action')">
+      {{ actionLabel }}
+      <Icon icon="vuesax-linear:arrow-left-2" size="15" />
+    </button>
+  </header>
+</template>
+
+<script setup lang="ts">
+import Icon from '../icon/Icon.vue'
+
+defineProps<{ title: string; subtitle?: string; actionLabel?: string }>()
+const emit = defineEmits<{ (e: 'action'): void }>()
+</script>
+
+<style scoped lang="less">
+.sec {
+  display: flex;
+  align-items: flex-end;
+  justify-content: space-between;
+  gap: 12px;
+  padding-bottom: 13px;
+}
+
+.sec__title {
+  margin: 0;
+  font-size: 15px;
+  font-weight: 800;
+  color: @ink;
+  letter-spacing: -0.1px;
+}
+
+.sec__sub {
+  margin: 5px 0 0;
+  font-size: 11.5px;
+  color: @inkFaint;
+}
+
+.sec__action {
+  display: inline-flex;
+  align-items: center;
+  gap: 4px;
+  border: 0;
+  background: none;
+  cursor: pointer;
+  padding: 0;
+  font-family: inherit;
+  font-size: 11.5px;
+  font-weight: 700;
+  color: @wine;
+  white-space: nowrap;
+}
+</style>