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/PoiDetailCard/index.vue

@@ -15,7 +15,7 @@
 
       <div class="poi-detail-card__tip flex flex-items-center gap-10">
         <div class="poi-detail-card__spark color-047857 font-size-18 font-900">✦</div>
-        <div class="poi-detail-card__tip-text color-047857 font-size-14 font-800">
+        <div class="poi-detail-card__tip-text color-047857 text-[14px] font-800">
           {{ data.tip?.text }}
         </div>
       </div>