style: 优化资产配置模块高度，使布局更紧凑

- 图表高度从 280px 降低到 200px
- 调整圆环大小和位置使其在较小空间内显示更协调
- 减少 CardBody 和详细配置信息的间距

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/views/TradingSimulation/components/AccountOverview.js

@@ -267,15 +267,15 @@ export default function AccountOverview({ account, tradingEvents }) {
             </Badge>
           </HStack>
         </CardHeader>
-        <CardBody>
+        <CardBody pt={0}>
           <AssetAllocationChart
             cashAmount={account?.availableCash || 0}
             stockAmount={account?.marketValue || 0}
-            height={280}
+            height={200}
           />
-          
+
           {/* 详细配置信息 */}
-          <VStack spacing={3} mt={4}>
+          <VStack spacing={2} mt={2}>
             <HStack justify="space-between" w="full">
               <HStack spacing={2}>
                 <Box w={3} h={3} bg="blue.400" borderRadius="sm" />

src/views/TradingSimulation/components/AssetAllocationChart.tsx

@@ -15,12 +15,12 @@ interface AssetAllocationChartProps {
  * 资产配置环形图
  * @param cashAmount - 现金资产金额
  * @param stockAmount - 股票资产金额
- * @param height - 图表高度，默认 280px
+ * @param height - 图表高度，默认 200px
  */
 export const AssetAllocationChart = ({
   cashAmount,
   stockAmount,
-  height = 280
+  height = 200
 }: AssetAllocationChartProps) => {
   const total = cashAmount + stockAmount;
 
@@ -48,7 +48,7 @@ export const AssetAllocationChart = ({
     },
     legend: {
       orient: 'horizontal',
-      bottom: 10,
+      bottom: 0,
       left: 'center',
       textStyle: {
         color: '#666',
@@ -62,8 +62,8 @@ export const AssetAllocationChart = ({
       {
         name: '资产配置',
         type: 'pie',
-        radius: ['45%', '70%'],
+        radius: ['40%', '65%'],
-        center: ['50%', '45%'],
+        center: ['50%', '42%'],
         avoidLabelOverlap: true,
         itemStyle: {
           borderRadius: 4,