feat(auth): implement option 3 architecture - server InteractiveServer login + client WASM dashboard

- Add Server.AddInteractiveServerComponents() + AddInteractiveServerRenderMode()
- Create Server AuthLayout for login form (MudBlazor)
- Implement LoginSimple.razor with @rendermode InteractiveServer in Server project
- Update App.razor: CascadingAuthenticationState + Router with AppAssembly=Server
- Fix Client MudBlazor Providers in MainLayout + AuthLayout
- Update Playwright tests: use dynamic selectors for MudTextField (auto-generated IDs)
- Build: 0 errors, 0 warnings
- API: /api/auth/login fully operational (200 OK confirmed)
- Playwright E2E test: 1 passed

Architecture:
/login    → Server InteractiveServer (MudBlazor form)
/         → Client WebAssembly (Dashboard)
/api/*    → Server Endpoints

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

src/dotnet/QuantEngine.Web/QuantEngine.Web.csproj

@@ -14,17 +14,23 @@
     <PackageReference Include="Hangfire.PostgreSql" Version="1.20.10" />
     <PackageReference Include="MudBlazor" Version="8.6.0" />
     <PackageReference Include="Serilog.AspNetCore" Version="10.0.0" />
-    <PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly.Server" Version="10.0.0-preview.2.25120.18" />
+    <PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly.Server" Version="10.0.0" />
   </ItemGroup>
 
   <ItemGroup>
     <!-- Exclude client project files from server build to avoid duplicate compilations -->
+    <!-- BUT preserve Client\wwwroot for static web assets -->
     <Compile Remove="Client\**" />
-    <Content Remove="Client\**" />
     <EmbeddedResource Remove="Client\**" />
     <None Remove="Client\**" />
   </ItemGroup>
 
+  <ItemGroup>
+    <!-- Only remove non-wwwroot Client content -->
+    <Content Remove="Client\**" />
+    <Content Include="Client\wwwroot\**" CopyToPublishDirectory="Never" />
+  </ItemGroup>
+
   <PropertyGroup>
     <TargetFramework>net10.0</TargetFramework>
     <Nullable>enable</Nullable>