ux: 花名册操作图标按钮分两行显示

第一行：调薪、转正、调部门
第二行：开具证明、续签合同、离职

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

frontend/src/pages/Roster.tsx

@@ -841,7 +841,8 @@ export default function Roster() {
                     </td>}
                     <td className="px-4 py-3 text-center">
                       {e.status === 'ACTIVE' && (!e.hasTermination || e.latestTerminationStatus === 'CANCELLED' || e.latestTerminationStatus === 'COMPLETED') && (
-                        <div className="flex items-center justify-center gap-2">
+                        <div className="flex flex-col items-center gap-1">
+                          <div className="flex items-center justify-center gap-1">
                             <button
                               type="button"
                               title="调薪"
@@ -884,6 +885,8 @@ export default function Roster() {
                             >
                               <Building2 className="h-4 w-4" />
                             </button>
+                          </div>
+                          <div className="flex items-center justify-center gap-1">
                             <button
                               type="button"
                               title="开具证明"
@@ -936,6 +939,7 @@ export default function Roster() {
                               <UserX className="h-4 w-4" />
                             </button>
                           </div>
+                        </div>
                       )}
                       {e.hasTermination && e.status === 'ACTIVE' && e.latestTerminationStatus !== 'CANCELLED' && e.latestTerminationStatus !== 'COMPLETED' && (
                         <div className="flex items-center justify-center gap-2">