style(index): update promo card price styling (¥98 yellow, larger font)

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

src/pages/index/index.vue

@@ -71,7 +71,7 @@
             <view class="promo-price-row">
               <view class="promo-price-block">
                 <text class="promo-currency">¥</text>
-                <text class="promo-price">198</text>
+                <text class="promo-price">98</text>
               </view>
               <view class="promo-value-block">
                 <text class="promo-value">¥3800+</text>
@@ -490,13 +490,13 @@ function goMore() {
 .promo-currency {
   font-size: $font-size-2xl;
   font-weight: $font-weight-bold;
-  color: #e53935;
+  color: #FFD600;
 }
 
 .promo-price {
-  font-size: 48rpx;
+  font-size: 144rpx;
   font-weight: $font-weight-bold;
-  color: #e53935;
+  color: #FFD600;
   line-height: 0.85;
   letter-spacing: -4rpx;
 }
@@ -515,7 +515,7 @@ function goMore() {
 }
 
 .promo-save {
-  font-size: $font-size-2xl;
+  font-size: 22rpx;
   color: #e53935;
   font-weight: $font-weight-bold;
   letter-spacing: 2rpx;