feat: [hr] 사원 등록/수정 - 비밀번호 제거 및 퇴직일 추가

- 비밀번호 필드 제거 (등록 폼, validation, 서비스)
- 퇴직일(resign_date) 필드 추가 (등록/수정/상세 화면)
- json_extra에 resign_date 저장/수정 지원
- Model에 resign_date accessor 추가

app/Http/Controllers/Api/Admin/HR/EmployeeController.php

@@ -76,7 +76,6 @@ public function store(Request $request): JsonResponse
             'name' => 'required|string|max:50',
             'email' => 'nullable|email|max:100',
             'phone' => 'nullable|string|max:20',
-            'password' => 'nullable|string|min:6',
             'department_id' => 'nullable|integer|exists:departments,id',
             'position_key' => 'nullable|string|max:50',
             'job_title_key' => 'nullable|string|max:50',
@@ -86,6 +85,7 @@ public function store(Request $request): JsonResponse
             'manager_user_id' => 'nullable|integer|exists:users,id',
             'display_name' => 'nullable|string|max:50',
             'hire_date' => 'nullable|date',
+            'resign_date' => 'nullable|date',
             'address' => 'nullable|string|max:200',
             'emergency_contact' => 'nullable|string|max:100',
         ];
@@ -154,6 +154,7 @@ public function update(Request $request, int $id): JsonResponse
             'manager_user_id' => 'nullable|integer|exists:users,id',
             'display_name' => 'nullable|string|max:50',
             'hire_date' => 'nullable|date',
+            'resign_date' => 'nullable|date',
             'address' => 'nullable|string|max:200',
             'emergency_contact' => 'nullable|string|max:100',
         ]);