feat: Phase 1-3 优化全部完成

Phase 1 紧急修复（8项）:
- 社保城市选择改为可输入
- 社保上下限拆分（三险/医保独立基数）
- 公积金试算结果展示修复
- 花名册合同保存修复（日期ISO格式）
- 薪酬批次创建失败修复（城市过滤+错误处理）
- 证据链查看修复
- 个税计算修复（blank_employees读取基本工资）
- 加班费倍率读取配置

Phase 2 功能完善（3项）:
- 批量导入per-row异常捕获+导入按钮
- 单人发薪UI入口优化
- 解除协议模板补充（员工提出离职版）

Phase 3 后期规划（4项）:
- 工资表导入功能（POST /import/payroll + 前端入口）
- 大病险/长护险附加险种（extraInsurances JSON + 计算适配）
- 专项附加扣除按月录入（SpecialDeductionRecord模型 + 前端Tab）
- 预置河北省社保政策（seed数据）

frontend/src/pages/roster/ContractInfo.tsx

@@ -175,7 +175,15 @@ export default function ContractInfo({ employeeId, contracts, hireDate }: { empl
               </>
             )}
             <div className="md:col-span-2 flex gap-2">
-              <Button onClick={() => addContractMutation.mutate(form)} disabled={
+              <Button onClick={() => {
+                const payload = {
+                  ...form,
+                  signDate: form.signDate ? new Date(form.signDate).toISOString() : null,
+                  startDate: new Date(form.startDate).toISOString(),
+                  endDate: form.endDate ? new Date(form.endDate).toISOString() : null,
+                }
+                addContractMutation.mutate(payload)
+              }} disabled={
                 addContractMutation.isPending || !form.startDate ||
                 (form.signMethod === 'PAPER' && !form.attachmentUrl) ||
                 (form.signMethod === 'ELECTRONIC' && (!form.electronicContractNo || !form.electronicContractUrl))

frontend/src/pages/roster/EmployeeProfile.tsx

@@ -12,6 +12,7 @@ import AttendanceOvertimeInfo from './AttendanceOvertimeInfo'
 import PerformanceInfo from './PerformanceInfo'
 import TerminationInfo from './TerminationInfo'
 import ChangeHistoryTab from './ChangeHistoryTab'
+import EvidenceChain from './EvidenceChain'
 
 /**
  * 员工详情档案页
@@ -99,6 +100,7 @@ export default function EmployeeProfile({ employeeId, onBack }: { employeeId: st
         {tab === 'attendance' && <AttendanceOvertimeInfo employeeId={employeeId} attendanceRecords={profile.attendanceRecords} overtimeRecords={profile.overtimeRecords} trainingRecords={profile.trainingRecords} />}
         {tab === 'performance' && <PerformanceInfo employeeId={employeeId} records={profile.performanceRecords} />}
         {tab === 'termination' && <TerminationInfo employeeId={employeeId} profile={profile} records={profile.terminations} />}
+        {tab === 'evidence' && <EvidenceChain employeeId={employeeId} />}
         {tab === 'history' && <ChangeHistoryTab profile={profile} />}
       </div>
     </div>

frontend/src/pages/roster/EvidenceChain.tsx

@@ -21,7 +21,22 @@ export default function EvidenceChain({ employeeId }: { employeeId: string }) {
   })
 
   if (isLoading) return <div className="text-center py-8 text-gray-400">生成证据链中...</div>
-  if (!data) return <div className="text-center py-8 text-gray-400">无数据</div>
+  if (!data) return <div className="text-center py-8 text-gray-400">暂无证据链数据，请确保员工已录入合同、薪酬等信息</div>
+  if (!data.evidence || data.evidence.length === 0) return (
+    <div className="space-y-3">
+      <Card>
+        <div className="flex items-center justify-between">
+          <div>
+            <h2 className="text-xs font-medium flex items-center gap-2"><Scale className="w-4 h-4" />仲裁证据链</h2>
+            <div className="text-xs text-gray-500 mt-1">
+              {data.employee?.name || '未知'} · {data.employee?.department || '未知'} · 入职{data.employee?.hireDate ? data.employee.hireDate.toString().slice(0, 10) : '未知'}
+            </div>
+          </div>
+        </div>
+      </Card>
+      <Card><div className="text-center py-8 text-gray-400">该员工暂无证据链记录，录入合同、薪酬、考勤等信息后将自动生成</div></Card>
+    </div>
+  )
 
   const categoryColor: Record<string, string> = {
     '劳动关系': 'bg-blue-50 text-blue-700 border-blue-200',

frontend/src/pages/roster/shared.ts

@@ -13,7 +13,7 @@ export const terminateReasonMap: Record<string, string> = {
 }
 
 /** 详情页 Tab 类型 */
-export type DetailTab = 'basic' | 'contract' | 'payslip' | 'attendance' | 'disciplinary' | 'performance' | 'termination' | 'history'
+export type DetailTab = 'basic' | 'contract' | 'payslip' | 'attendance' | 'disciplinary' | 'performance' | 'termination' | 'evidence' | 'history'
 
 /** Tab 分组 */
 export type TabGroup = '人事信息' | '考勤绩效' | '风险合规' | '薪酬' | '变更历史'
@@ -45,6 +45,7 @@ export const TAB_GROUPS: { group: TabGroup; tabs: { key: DetailTab; label: strin
     tabs: [
       { key: 'disciplinary', label: '违纪记录', icon: null },
       { key: 'termination', label: '离职/解聘', icon: null },
+      { key: 'evidence', label: '证据链', icon: null },
     ],
   },
   {