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/components/DetailPopup/index.vue

@@ -12,11 +12,11 @@
       <div class="rounded-12 bg-white ml-12 mr-12 mb-40">
         <div class="border-box border-bottom flex flex-items-center flex-justify-between pt-12 pb-12 ml-12 mr-12">
           <span class="font-size-16 font-500 color-171717">在线支付</span>
-          <span class="font-size-14 color-171717">239</span>
+          <span class="text-[14px] color-171717">239</span>
         </div>
         <div class="border-box flex flex-items-center flex-justify-between pt-12 pb-12 ml-12 mr-12">
           <span class="font-size-16 font-500 color-171717">房费</span>
-          <span class="font-size-14 color-171717">239</span>
+          <span class="text-[14px] color-171717">239</span>
         </div>
       </div>
     </div>