feat: standalone Blazor WebAssembly admin + SEO enhancements

Architecture:
- Admin UI: /admin (Standalone Blazor WebAssembly, 219 WASM files)
- Portal: /portal (Razor Pages, Cookie/OAuth auth)
- Homepage: / (Razor Pages, SSR)
- API: /api (FastEndpoints + JWT)

SEO:
- Sitemap: Public content only (blog, FAQ, announcements, contact)
- robots.txt: Exclude /admin and /portal, reference production domain
- Naver verification: naverb1813cd79ddc2ded5c5291fca5cb46c2.html ready

Technical:
- TaxBaik.Web.Client: StaticWebAssetBasePath=admin
- Server Program.cs: UseBlazorFrameworkFiles + MapFallback for SPA routing
- base href="/admin/" for client-side navigation
- blazor.webassembly.js (standalone, not web.js)

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

src/TaxBaik.Web.Client/Components/Admin/Pages/Blog/BlogCreate.razor

@@ -0,0 +1,66 @@
+@page "/admin/blog/create"
+@rendermode @(new InteractiveWebAssemblyRenderMode(prerender: false))
+@attribute [Authorize]
+@using TaxBaik.Application.DTOs
+@using TaxBaik.WasmClient.Components.Admin.Pages.Blog
+@inject IBlogBrowserClient BlogClient
+@inject ICategoryBrowserClient CategoryClient
+@inject NavigationManager Navigation
+@inject ISnackbar Snackbar
+
+<PageTitle>새 포스트 작성</PageTitle>
+
+<AdminCrudPageShell Title="새 포스트 작성"
+                    Eyebrow="Content"
+                    Subtitle="새로운 블로그 포스트를 작성합니다."
+                    Loading="@false"
+                    OnCancel="@GoBack">
+    <MudPaper Class="pa-4 mt-4" Elevation="1">
+        <BlogForm Model="model" Categories="categories" SubmitText="저장" OnSubmit="SavePost" OnCancel="GoBack" />
+    </MudPaper>
+</AdminCrudPageShell>
+
+@code {
+    private IReadOnlyList<Domain.Entities.Category> categories = [];
+    private BlogForm.BlogFormModel model = new();
+
+    protected override async Task OnInitializedAsync()
+    {
+        categories = await CategoryClient.GetAllAsync();
+    }
+
+    private void GoBack()
+    {
+        Navigation.NavigateTo("/taxbaik/admin/blog");
+    }
+
+    private async Task SavePost()
+    {
+        try
+        {
+            var result = await BlogClient.CreateAsync(new CreateBlogPostDto
+            {
+                Title = model.Title,
+                Content = model.Content,
+                CategoryId = model.CategoryId,
+                Tags = model.Tags,
+                SeoTitle = model.SeoTitle,
+                SeoDescription = model.SeoDescription,
+                IsPublished = model.IsPublished
+            });
+
+            if (result == null)
+            {
+                Snackbar.Add("포스트 저장에 실패했습니다.", Severity.Error);
+                return;
+            }
+
+            Snackbar.Add("포스트가 저장되었습니다.", Severity.Success);
+            Navigation.NavigateTo("/taxbaik/admin/blog");
+        }
+        catch (ValidationException ex)
+        {
+            Snackbar.Add(ex.Message, Severity.Error);
+        }
+    }
+}