fix(admin-web): 过滤掉不存在的固定系统账户

- 添加 filter 过滤掉 data 为 null 的账户
- 修复空白卡片显示问题（账户数据不存在时不显示卡片）

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/admin-web/src/components/features/system-account-report/SystemAccountsTab.tsx

@@ -300,7 +300,7 @@ export default function SystemAccountsTab() {
  * [2026-01-07] 更新：添加查看分类账明细按钮，在卡片下方公共区域显示明细
  */
 function FixedAccountsSection({ data }: { data: SystemAccountReportResponse['fixedAccounts'] }) {
-  // [2026-01-07] 修复：从后端返回数据中读取真实的 accountSequence，而不是硬编码
+  // [2026-01-07] 修复：从后端返回数据中读取真实的 accountSequence，过滤掉不存在的账户
   // 后端映射：S0000000001=HQ_COMMUNITY, S0000000002=COST_ACCOUNT, S0000000003=OPERATION_ACCOUNT
   const accounts = [
     { key: 'costAccount', data: data.costAccount },
@@ -308,10 +308,12 @@ function FixedAccountsSection({ data }: { data: SystemAccountReportResponse['fix
     { key: 'hqCommunity', data: data.hqCommunity },
     { key: 'rwadPoolPending', data: data.rwadPoolPending },
     { key: 'platformFee', data: data.platformFee },
-  ].map(item => ({
-    ...item,
-    sequence: item.data?.accountSequence || '',
-  }));
+  ]
+    .filter(item => item.data !== null && item.data !== undefined) // 过滤掉不存在的账户
+    .map(item => ({
+      ...item,
+      sequence: item.data?.accountSequence || '',
+    }));
 
   // [2026-01-07] 新增：选中账户和分类账数据
   const [selectedAccount, setSelectedAccount] = useState<string | null>(null);