refactor: Update UserFormModal to remove department code requirement

- Modified the user form validation logic to make the department code optional in edit mode.
- Removed the department code from the required fields check and adjusted the UI label accordingly.
- Ensured that the form validation still checks for email format when provided.

frontend/components/admin/UserFormModal.tsx

@@ -145,13 +145,12 @@ export function UserFormModal({ isOpen, onClose, onSuccess, editingUser }: UserF
   const isFormValid = useMemo(() => {
     // 수정 모드에서는 비밀번호 선택 사항 (변경할 경우만 입력)
     const requiredFields = isEditMode
-      ? [formData.userId.trim(), formData.userName.trim(), formData.companyCode, formData.deptCode]
+      ? [formData.userId.trim(), formData.userName.trim(), formData.companyCode]
       : [
           formData.userId.trim(),
           formData.userPassword.trim(),
           formData.userName.trim(),
           formData.companyCode,
-          formData.deptCode,
         ];
 
     // 모든 필수 필드가 입력되었는지 확인
@@ -327,11 +326,6 @@ export function UserFormModal({ isOpen, onClose, onSuccess, editingUser }: UserF
       return false;
     }
 
-    if (!formData.deptCode) {
-      showAlert("입력 오류", "부서를 선택해주세요.", "error");
-      return false;
-    }
-
     // 이메일 형식 검사 (입력된 경우만)
     if (formData.email && !/^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(formData.email)) {
       showAlert("입력 오류", "올바른 이메일 형식을 입력해주세요.", "error");
@@ -581,7 +575,7 @@ export function UserFormModal({ isOpen, onClose, onSuccess, editingUser }: UserF
             <div className="grid grid-cols-2 gap-4">
               <div className="space-y-2">
                 <Label htmlFor="deptCode" className="text-sm font-medium">
-                  부서 <span className="text-red-500">*</span>
+                  부서
                 </Label>
                 <Select value={formData.deptCode} onValueChange={(value) => handleInputChange("deptCode", value)}>
                   <SelectTrigger>