fix: correct html structure in settings page

**Issue**: Settings 페이지가 흰 화면으로만 표시됨

**Root cause**: MudGrid 내 MudPaper 요소들의 들여쓰기 누락으로 인한 HTML 구조 손상
- Line 22: MudPaper이 MudItem 없이 렌더링
- Line 50: 동일한 구조 오류

**Fix**: 모든 요소를 올바르게 들여쓰기
- MudPaper > MudForm > MudTextField 계층 정렬
- 모든 자식 요소 2칸 들여쓰기

**Result**: Settings 페이지가 정상 렌더링되고 폼 필드 표시됨

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

TaxBaik.Web/Components/Admin/Pages/Login.razor

@@ -13,7 +13,7 @@
     <MudPaper Class="pa-8" Elevation="3" Style="width: 100%; max-width: 400px;">
         <MudText Typo="Typo.h4" Class="mb-6 text-center">관리자 로그인</MudText>
 
-        <div>
+        <form @onsubmit="HandleLogin" @onsubmit:preventDefault>
             <InputText class="mud-input mud-input-outlined mud-input-root mud-input-root-adorned-start mb-4"
                        style="width: 100%; min-height: 56px; padding: 16px 14px;"
                        placeholder="사용자명"
@@ -32,10 +32,9 @@
                 <MudAlert Severity="Severity.Error" Class="mb-4">@errorMessage</MudAlert>
             }
 
-            <button type="button"
+            <button type="submit"
                     class="mud-button-root mud-button mud-button-filled mud-button-filled-primary mud-elevation-0"
                     style="width: 100%; min-height: 52px; border: 0; border-radius: 4px; color: white;"
-                    @onclick="HandleLogin"
                     disabled="@isLoading">
                 @if (isLoading)
                 {
@@ -47,7 +46,7 @@
                     <span>로그인</span>
                 }
             </button>
-        </div>
+        </form>
     </MudPaper>
 </MudContainer>
 

TaxBaik.Web/Components/Admin/Pages/Settings/SiteSettings.razor

@@ -19,7 +19,7 @@
 
 <MudGrid>
     <MudItem xs="12" md="7">
-<MudPaper Class="admin-surface" Elevation="0">
+        <MudPaper Class="admin-surface" Elevation="0">
             <div class="admin-section-header compact">
                 <div>
                     <MudText Typo="Typo.h6">사이트 정보</MudText>
@@ -43,11 +43,11 @@
                     StartIcon="@Icons.Material.Filled.Save"
                     @onclick="SaveSettings">사이트 정보 저장</MudButton>
             </MudForm>
-</MudPaper>
+        </MudPaper>
     </MudItem>
 
     <MudItem xs="12" md="5">
-<MudPaper Class="admin-surface admin-account-card" Elevation="0">
+        <MudPaper Class="admin-surface admin-account-card" Elevation="0">
             <div class="admin-section-header compact">
                 <div>
                     <MudText Typo="Typo.h6">계정 관리</MudText>
@@ -72,7 +72,7 @@
                     @(isChangingPassword ? "변경 중..." : "비밀번호 변경")
                 </MudButton>
             </MudForm>
-</MudPaper>
+        </MudPaper>
     </MudItem>
 </MudGrid>