fix: 桑基图标题位置调整，避免被图表遮挡

- 标题 top 调整为 5
- 桑基图 series 添加 top: 50 给标题留出空间
- 添加 bottom, left, right 边距配置

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

src/views/EventDetail/components/TransmissionChainAnalysis.js

@@ -349,7 +349,7 @@ function getSankeyOption(data) {
     title: {
       text: '事件影响力传导流向',
       left: 'center',
-      top: 10,
+      top: 5,
       textStyle: {
         color: '#00d2d3',
         fontSize: 16,
@@ -379,6 +379,10 @@ function getSankeyOption(data) {
     series: [{
       type: 'sankey',
       layout: 'none',
+      top: 50,      // 给标题留出空间
+      bottom: 20,
+      left: 20,
+      right: 150,   // 右侧留空间给标签
       emphasis: { focus: 'adjacency' },
       nodeAlign: 'justify',
       layoutIterations: 0,