fix: 修复几何复杂度分析结果表格头部滚动时背景透明问题

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

src/components/pages/GeometryComplexityResult.vue

@@ -440,7 +440,7 @@ onMounted(() => {
 }
 
 .complexity-parts-table th {
-  background: var(--color-complexity-bg-2);
+  background: var(--color-bg-secondary);
   color: var(--color-complexity);
   padding: var(--spacing-sm) var(--spacing-md);
   text-align: left;
@@ -448,7 +448,8 @@ onMounted(() => {
   border-bottom: 1px solid var(--color-complexity-border-2);
   position: sticky;
   top: 0;
-  z-index: 1;
+  z-index: 10;
+  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
 }
 
 .complexity-parts-table td {