refactor: replace theme color utility classes with direct hex values

remove unused theme color background utility classes from background.scss,
swap all instances of bg-theme-color-50 and bg-theme-color-500 with their
corresponding hex values across vue components, and update bg-liner gradient
to use direct hex colors instead of theme variables

src/components/CreateServiceOrder/index.vue

@@ -1,7 +1,7 @@
 <template>
   <view class="create-service-order">
     <view class="w-full bg-white border-box border-ff overflow-hidden rounded-20">
-      <view class="border-box order-header w-vw flex flex-items-center flex-justify-between bg-theme-color-50">
+      <view class="border-box order-header w-vw flex flex-items-center flex-justify-between bg-[#F0F8F3]">
         <text class="font-size-18 font-500 color-171717 text-left ml-[12px]">
           {{ isCallSuccess ? "服务已创建" : "呼叫服务" }}
         </text>