style: migrate font-size classes to text-[size] syntax

Additionally update spacing utilities and refactor the OrderQrcode component:
- Switch popup implementation from uni-popup to van-popup
- Remove the deprecated SCSS stylesheet
- Clean up component template and script code

src/pages/home/components/SharedVisual/DetailShell.vue

@@ -5,7 +5,7 @@
         @click="$emit('back')">
         <uni-icons type="left" size="16" color="#CBD5E1"></uni-icons>
       </div>
-      <div class="visual-detail__title flex-full color-1E293B font-size-14 font-900 ellipsis-1">{{ title }}</div>
+      <div class="visual-detail__title flex-full color-1E293B text-[14px] font-900 ellipsis-1">{{ title }}</div>
       <BadgePill v-if="tag" :label="tag" :tone="tone" />
     </div>
     <slot />