feat: 사원-회원 연결 기능 구현 (Phase 2 API)

- store() 수정: create_account=false면 password=NULL 허용 (사원 전용)
- revokeAccount() 추가: 시스템 계정 해제 (password=NULL, 토큰 무효화)
- POST /employees/{id}/revoke-account 라우트 추가
- ko/employee.php, en/employee.php 언어 파일 생성

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

routes/api.php

@@ -286,6 +286,7 @@
             Route::delete('/{id}', [EmployeeController::class, 'destroy'])->name('v1.employees.destroy');
             Route::post('/bulk-delete', [EmployeeController::class, 'bulkDelete'])->name('v1.employees.bulkDelete');
             Route::post('/{id}/create-account', [EmployeeController::class, 'createAccount'])->name('v1.employees.createAccount');
+            Route::post('/{id}/revoke-account', [EmployeeController::class, 'revokeAccount'])->name('v1.employees.revokeAccount');
         });
 
         // Attendance API (근태 관리)