feat: 解聘补偿增加「模拟计算」按钮 — 只计算不实际保存

- Step 4 费用结算增加「模拟计算」按钮
- 点击后计算补偿金并暂存到右侧列表，重置向导
- 不调用保存接口，不创建解聘记录
- 「确认保存」仍走原有流程保存到后端

frontend/src/pages/Termination.tsx

@@ -294,6 +294,53 @@ export default function Termination() {
     })
   }
 
+  // 模拟计算：只计算并暂存，不实际保存解聘记录
+  const handleSimulate = () => {
+    if (!costResult || !selectedEmployee) return
+    setSavedItems((prev) => {
+      if (prev.some((item) => item.employeeId === employeeId)) {
+        return prev.map((item) =>
+          item.employeeId === employeeId
+            ? {
+                employeeId,
+                name: selectedEmployee.name,
+                department: selectedEmployee.department,
+                reason,
+                reasonLabel,
+                terminationDate,
+                severancePay: costResult.severancePay,
+                noticePay: costResult.noticePay,
+                doublePay: costResult.doublePay,
+                grandTotal: costResult.grandTotal,
+                years: costResult.years,
+                remainingMonths: costResult.remainingMonths,
+                compMonths: costResult.compMonths,
+              }
+            : item
+        )
+      }
+      return [
+        ...prev,
+        {
+          employeeId,
+          name: selectedEmployee.name,
+          department: selectedEmployee.department,
+          reason,
+          reasonLabel,
+          terminationDate,
+          severancePay: costResult.severancePay,
+          noticePay: costResult.noticePay,
+          doublePay: costResult.doublePay,
+          grandTotal: costResult.grandTotal,
+          years: costResult.years,
+          remainingMonths: costResult.remainingMonths,
+          compMonths: costResult.compMonths,
+        },
+      ]
+    })
+    handleReset()
+  }
+
   // 保存成功后暂存到右侧列表
   useEffect(() => {
     if (saveMutation.isSuccess && costResult && selectedEmployee) {
@@ -816,9 +863,14 @@ export default function Termination() {
                 下一步<ChevronRight className="w-4 h-4 ml-1" />
               </Button>
             ) : (
+              <div className="flex gap-2">
+                <Button variant="secondary" onClick={handleSimulate}>
+                  <Calculator className="w-4 h-4 mr-1" />模拟计算
+                </Button>
                 <Button onClick={handleSave} disabled={saveMutation.isPending}>
                   <Shield className="w-4 h-4 mr-1" />确认保存
                 </Button>
+              </div>
             )}
           </div>
         )}