fix: restore AddAdditionalAssemblies - required for WASM component discovery

Root component alone cannot load all routed WASM components.
AddAdditionalAssemblies is essential for:
- App.razor discovery
- Routes.razor registration
- All Page components in TaxBaik.WasmClient assembly

This fixes the ObjectDisposedException and Kestrel binding failures.

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

TaxBaik.Web/Program.cs

@@ -392,10 +392,10 @@ app.MapStaticAssets();
 // Phase 8: WebAssembly 렌더 모드 완전 마이그레이션
 // - App.razor: TaxBaik.WasmClient (호스트, WebAssembly)
 // - Routes + Pages + Shared + Layout + Forms: TaxBaik.WasmClient (WebAssembly)
-// MapRazorComponents<TaxBaik.WasmClient.Components.Admin.App>()가 이미 어셈블리 포함하므로
-// AddAdditionalAssemblies 불필요 (중복 시 "Assembly already defined" 에러 발생)
+// AddAdditionalAssemblies는 필수: App.razor만으로는 모든 라우트된 컴포넌트를 찾을 수 없음
 app.MapRazorComponents<TaxBaik.WasmClient.Components.Admin.App>()
    .AddInteractiveWebAssemblyRenderMode()
+   .AddAdditionalAssemblies(typeof(TaxBaik.WasmClient._Imports).Assembly)
    .AllowAnonymous();
 
 // 애플리케이션 시작/종료 로깅