fix: resolve admin interactivity by unifying to Server render mode

Problem: Mixed WebAssembly (App) and Server (Login) render modes caused interaction breakage after login. Panels, accordions, and menu selections failed because render mode changed during page navigation.

Solution: Unified all admin components to InteractiveServerRenderMode for consistent interactivity:
- App.razor: Routes and HeadOutlet use InteractiveServerRenderMode
- Login.razor: Already uses InteractiveServerRenderMode
- Program.cs: Removed WebAssembly component registration

Updated validation script to require Server mode instead of WebAssembly for admin shell.

This ensures:
✅ Consistent render mode throughout admin UI
✅ Reliable component interactivity (panels, accordions, menus)
✅ Stable page navigation and state management

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

TaxBaik.Web/Components/Admin/App.razor

@@ -37,7 +37,7 @@
         </div>
     </div>
     <MudThemeProvider @bind-IsDarkMode="isDarkMode" Theme="mudTheme" />
-    <Routes @rendermode="new InteractiveWebAssemblyRenderMode(prerender: true)" />
+    <Routes @rendermode="new InteractiveServerRenderMode(prerender: true)" />
     <script src="/taxbaik/_content/MudBlazor/MudBlazor.min.js"></script>
     <script src="/taxbaik/js/admin-session.js"></script>
     <script src="/taxbaik/_framework/blazor.web.js"></script>