fix: use Blazor Server render mode instead of WebAssembly

- Change from AddInteractiveWebAssemblyRenderMode() to AddInteractiveServerRenderMode()
- Project structure doesn't support WebAssembly hosting model yet
- Server render mode uses existing Blazor Server infrastructure
- Fixes 404 errors and infinite loading screen

This is a temporary fix to restore admin functionality.
WebAssembly migration can be done in a separate phase with proper project restructuring.

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

src/TaxBaik.Web/Program.cs

@@ -427,8 +427,7 @@ app.MapStaticAssets();
 // 모든 Blazor 컴포넌트가 웹 서버에서 통합 서비스됨
 // API는 웹 서버에서만 제공 (클라이언트 프로젝트 분리 불필요)
 app.MapRazorComponents<TaxBaik.Web.Components.Admin.App>()
-   .AddInteractiveWebAssemblyRenderMode()
+   .AddInteractiveServerRenderMode()
-   .AddAdditionalAssemblies(typeof(TaxBaik.Web.Components.Admin._Imports).Assembly)
    .AllowAnonymous();
 
 // 애플리케이션 시작/종료 로깅