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/Pages/Sitemap.cshtml.cs

@@ -15,16 +15,31 @@ public class SitemapModel : PageModel
 
     public async Task OnGetAsync()
     {
-        var baseUrl = "http://178.104.200.7/taxbaik";
+        // 프로덕션 도메인 기본값 (배포 환경에서 자동 감지 가능)
+        var baseUrl = $"{Request.Scheme}://{Request.Host.Value}/taxbaik";
+
+        // 정적 페이지 (공개 콘텐츠만)
         Urls.AddRange(new[]
         {
+            // 홈페이지
             $"{baseUrl}",
             $"{baseUrl}/about",
             $"{baseUrl}/services",
             $"{baseUrl}/contact",
-            $"{baseUrl}/blog"
+            $"{baseUrl}/privacy",
+            $"{baseUrl}/terms",
+
+            // 공개 콘텐츠
+            $"{baseUrl}/blog",
+            $"{baseUrl}/faq",
+            $"{baseUrl}/announcement",
+            $"{baseUrl}/inquiry"
+
+            // 제외: /admin (관리자), /portal (고객 포탈)
+            // robots.txt에서도 disallow
         });
 
+        // 동적 페이지: 블로그 포스트
         var (posts, _) = await _blogService.GetPublishedPagedAsync(1, 1000);
         foreach (var post in posts)
         {