fix: inquiry edit form - make customer fields read-only

P1-04: Inquiry 수정 계약 확정 - 화면과 저장 필드 불일치 제거

Problem: InquiryEdit showed editable fields for Name/Phone/Email/Message, but
UpdateInquiryDto only saved Status/AdminMemo. Users could edit fields that had
no effect on save - the 'false affordance' anti-pattern.

Solution:
- Add IsEditMode parameter to InquiryForm
- When IsEditMode=true: bind Name/Phone/Email/Message as ReadOnly (disabled input)
- Update InquiryEdit to pass IsEditMode="true"
- InquiryCreate passes default false, keeping all fields editable

Result: Edit mode now clearly shows which fields are modifiable (Status, AdminMemo)
vs. informational (customer contact details, message text). UI matches API contract.

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

src/TaxBaik.Web.Client/Components/Admin/Forms/InquiryForm.razor

@@ -5,20 +5,20 @@
 <MudForm @ref="form">
     <AdminFormSection Title="연락처" Description="고객 식별과 기본 회신 정보입니다." CssClass="mb-4">
         <MudTextField @bind-Value="model.Name" Label="이름"
-            Variant="Variant.Outlined" Class="mb-4" Required="true" />
+            Variant="Variant.Outlined" Class="mb-4" Required="true" ReadOnly="@IsEditMode" />
 
         <MudTextField @bind-Value="model.Phone" Label="전화번호 (예: 010-1234-5678)"
-            Variant="Variant.Outlined" Class="mb-4" Required="true" />
+            Variant="Variant.Outlined" Class="mb-4" Required="true" ReadOnly="@IsEditMode" />
 
         <MudTextField @bind-Value="model.Email" Label="이메일"
-            Variant="Variant.Outlined" Class="mb-4" InputType="InputType.Email" />
+            Variant="Variant.Outlined" Class="mb-4" InputType="InputType.Email" ReadOnly="@IsEditMode" />
     </AdminFormSection>
 
-    <AdminFormSection Title="문의 내용" Description="운영 분류와 처리 메모를 함께 관리합니다." CssClass="mb-4">
-        <CommonCodeSelect @bind-Value="model.ServiceType" Group="INQUIRY_SERVICE_TYPE" Label="문의 유형" Class="mb-4" />
+    <AdminFormSection Title="문의 내용" Description="@(IsEditMode ? "상태와 메모만 변경 가능합니다." : "운영 분류와 처리 메모를 함께 관리합니다.")" CssClass="mb-4">
+        <CommonCodeSelect @bind-Value="model.ServiceType" Group="INQUIRY_SERVICE_TYPE" Label="문의 유형" Class="mb-4" Disabled="@IsEditMode" />
 
         <MudTextField @bind-Value="model.Message" Label="문의 내용"
-            Variant="Variant.Outlined" Lines="5" Class="mb-4" Required="true" />
+            Variant="Variant.Outlined" Lines="5" Class="mb-4" Required="true" ReadOnly="@IsEditMode" />
 
         <CommonCodeSelect @bind-Value="model.Status" Group="INQUIRY_STATUS" Label="상태" Class="mb-4" />
 
@@ -48,6 +48,9 @@
     [Parameter]
     public InquiryFormModel? InitialData { get; set; }
 
+    [Parameter]
+    public bool IsEditMode { get; set; } = false;
+
     private MudForm? form;
     private InquiryFormModel model = new();
     protected override async Task OnInitializedAsync()

src/TaxBaik.Web.Client/Components/Admin/Pages/Inquiries/InquiryEdit.razor

@@ -23,7 +23,7 @@
 else
 {
     <MudPaper Class="pa-4 mt-4" Elevation="1">
-        <InquiryForm ButtonText="수정" InitialData="formModel" OnSubmit="HandleUpdate" OnCancel="GoBack" />
+        <InquiryForm ButtonText="수정" InitialData="formModel" OnSubmit="HandleUpdate" OnCancel="GoBack" IsEditMode="true" />
 
         <MudDivider Class="my-4" />