fix(前端): 修复成员表头与加班导出

关键改动：

- 成员管理表格改为卡片内滚动，并固定每个表头单元格

- 加班导出按当前月份筛选导出记录

- 增加成员表头与加班导出月份过滤测试

Co-Authored-By: Codex GPT-5 <codex@openai.com>

apps/web/lib/member-page-header.test.ts

@@ -0,0 +1,28 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { readFileSync } from 'node:fs';
+import { join } from 'node:path';
+
+test('members table pins each header cell above scrolling rows', () => {
+  const source = readFileSync(join(process.cwd(), 'app/admin/members/page.tsx'), 'utf8');
+  const headerClassNames = Array.from(
+    source.matchAll(/<th className="([^"]+)">/g),
+    (match) => match[1],
+  );
+
+  assert.equal(headerClassNames.length, 6);
+  for (const className of headerClassNames) {
+    assert.match(className, /\bsticky\b/);
+    assert.match(className, /\btop-0\b/);
+    assert.match(className, /\bz-20\b/);
+    assert.match(className, /bg-\[var\(--bg-subtle\)\]/);
+  }
+});
+
+test('members table scrolls inside the table card instead of the padded page area', () => {
+  const source = readFileSync(join(process.cwd(), 'app/admin/members/page.tsx'), 'utf8');
+
+  assert.match(source, /className="flex-1 overflow-hidden bg-\[var\(--bg\)\] px-5 py-4"/);
+  assert.match(source, /className="h-full overflow-hidden rounded-2xl border border-\[var\(--line\)\] bg-\[var\(--bg-card\)\] shadow-\[var\(--shadow-sm\)\]"/);
+  assert.match(source, /className="h-full overflow-y-auto"/);
+});