fix: restore Blazor WebAssembly render mode for ERP scalability

Restore long-term architectural goal: Blazor WebAssembly for admin UI.

Rationale:
- TaxBaik is a semi-project for future ERP implementation
- ERP requires client-side scalability (no server-side state per user)
- WebAssembly offloads interactivity to browser (Circuit-free)
- Aligns with API-First + stateless backend design

Changes:
- App.razor: InteractiveWebAssemblyRenderMode (prerender: true)
- Routes: InteractiveWebAssemblyRenderMode (prerender: true)
- Login.razor: InteractiveWebAssemblyRenderMode (prerender: true)
- Program.cs: AddInteractiveWebAssemblyComponents()
- Updated validation script to enforce WebAssembly mode

Tradeoff accepted: Blazor WebAssembly bootstrap time vs future ERP extensibility.

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

TaxBaik.Web/Program.cs

@@ -71,10 +71,10 @@ builder.Services.AddRateLimiter(options =>
     });
 });
 
-// Razor Pages + Blazor Server 통합
+// Razor Pages + Blazor WebAssembly 통합
 builder.Services.AddRazorPages();
 builder.Services.AddRazorComponents()
-    .AddInteractiveServerComponents();
+    .AddInteractiveWebAssemblyComponents();
 builder.Services.Configure<Microsoft.AspNetCore.Components.Server.CircuitOptions>(options =>
 {
     options.DetailedErrors = true;
@@ -389,7 +389,8 @@ app.MapStaticAssets();
 // AllowAnonymous: JWT 미들웨어가 Blazor 셸 요청을 401로 차단하지 않도록 한다.
 // 인증은 Blazor AuthorizeRouteView → RedirectToLogin 에서 처리한다.
 app.MapRazorComponents<TaxBaik.Web.Components.Admin.App>()
-   .AddInteractiveServerRenderMode()
+   .AddInteractiveWebAssemblyRenderMode()
+   .AddAdditionalAssemblies(typeof(TaxBaik.WasmClient._Imports).Assembly)
    .AllowAnonymous();
 
 // 애플리케이션 시작/종료 로깅