fix: 站点账户卡片头部余额字段修正为 availableBalance

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

admin-h5/src/pages/finance/index.vue

@@ -86,8 +86,8 @@
               <text class="station-id">站点ID: {{ account.stationId }}</text>
             </view>
             <view class="account-balance">
-              <text class="balance-label">账户余额:</text>
-              <text class="balance-value">¥{{ formatAmount(account.balance || 0) }}</text>
+              <text class="balance-label">可提现金额:</text>
+              <text class="balance-value">¥{{ formatAmount(account.availableBalance || 0) }}</text>
             </view>
           </view>
           <view class="account-content">