style: Apply Tabler layout to Blog create/edit pages

- Add admin-page-shell wrapper and _AdminPageHeader partial
- Wrap editor content in card component
- Consistent with other admin pages (Index.cshtml pattern)

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

src/TaxBaik.Web/Pages/Admin/Blog/Create.cshtml

@@ -5,7 +5,12 @@
     ViewData["BlogCategories"] = Model.Categories;
 }
 
-@await Html.PartialAsync("_BlogEditor", new TaxBaik.Web.Pages.Shared.BlogEditorModel(
+<section class="admin-page-shell">
+    @await Html.PartialAsync("_AdminPageHeader", new TaxBaik.Web.Models.AdminPageHeaderModel("콘텐츠", "새 글 작성", "블로그 글을 등록합니다.", null, null))
+
+    <div class="card">
+        <div class="card-body">
+            @await Html.PartialAsync("_BlogEditor", new TaxBaik.Web.Pages.Shared.BlogEditorModel(
                 Model.Input.Title,
                 Model.Input.Content,
                 Model.Input.CategoryId,
@@ -14,6 +19,9 @@
                 Model.Input.SeoTitle,
                 Model.Input.SeoDescription,
                 false))
+        </div>
+    </div>
+</section>
 
 @section Scripts {
     <script src="~/js/admin-blog-editor.js" asp-append-version="true"></script>

src/TaxBaik.Web/Pages/Admin/Blog/Edit.cshtml

@@ -6,7 +6,12 @@
     ViewData["BlogCategories"] = Model.Categories;
 }
 
-@await Html.PartialAsync("_BlogEditor", new TaxBaik.Web.Pages.Shared.BlogEditorModel(
+<section class="admin-page-shell">
+    @await Html.PartialAsync("_AdminPageHeader", new TaxBaik.Web.Models.AdminPageHeaderModel("콘텐츠", "글 수정", "블로그 글을 수정합니다.", null, null))
+
+    <div class="card">
+        <div class="card-body">
+            @await Html.PartialAsync("_BlogEditor", new TaxBaik.Web.Pages.Shared.BlogEditorModel(
                 Model.Input.Title,
                 Model.Input.Content,
                 Model.Input.CategoryId,
@@ -16,6 +21,9 @@
                 Model.Input.SeoDescription,
                 true,
                 "?handler=Delete"))
+        </div>
+    </div>
+</section>
 
 @section Scripts {
     <script src="~/js/admin-blog-editor.js" asp-append-version="true"></script>