feat: 组合卡片显示今日涨跌额

- 当前估值使用组合原始币种
- 新增今日变动行（如有数据）

pages/index/index.vue

@@ -113,13 +113,20 @@
         <view class="card-bottom">
           <view class="data-col">
             <text class="data-label">当前估值</text>
-            <text class="data-val">¥ {{ (holding.value || 0).toLocaleString('zh-CN', { minimumFractionDigits: 2, maximumFractionDigits: 2 }) }}</text>
+            <text class="data-val">{{ getCurrencySymbol(holding.currency) }}{{ (holding.value || 0).toLocaleString('zh-CN', { minimumFractionDigits: 2, maximumFractionDigits: 2 }) }}</text>
           </view>
           <view class="data-col align-right">
             <text class="data-label">历史总变动</text>
             <text class="data-val" :class="holding.returnType === 'positive' ? 'text-red' : 'text-green'">{{ (holding.returnRate || 0) >= 0 ? '+' : '' }}{{ holding.returnRate || 0 }}%</text>
           </view>
         </view>
+        
+        <view class="card-extra" v-if="holding.todayProfit">
+          <text class="extra-label">今日变动</text>
+          <text class="extra-val" :class="(holding.todayProfit || 0) >= 0 ? 'text-red' : 'text-green'">
+            {{ (holding.todayProfit || 0) >= 0 ? '+' : '' }}{{ getCurrencySymbol(holding.todayProfitCurrency || holding.currency) }}{{ Math.abs(holding.todayProfit || 0).toLocaleString('zh-CN', { minimumFractionDigits: 2, maximumFractionDigits: 2 }) }}
+          </text>
+        </view>
       </view>
 
       <view style="height: 100rpx;"></view>
@@ -659,4 +666,24 @@ onShow(async () => {
   font-family: 'DIN Alternate', sans-serif;
   color: #1F2937;
 }
+
+.card-extra {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  margin-top: 16rpx;
+  padding-top: 16rpx;
+  border-top: 1rpx solid #F3F4F6;
+}
+
+.extra-label {
+  font-size: 22rpx;
+  color: #9CA3AF;
+}
+
+.extra-val {
+  font-size: 28rpx;
+  font-weight: 600;
+  font-family: 'DIN Alternate', sans-serif;
+}
 </style>