Initial Blazor Web App template

Rider-generated Blazor Web App (net10.0, interactive render mode None,
no auth scaffold, no sample pages). Includes Rider auto-formatting.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Elternbeirat.Web/Elternbeirat.Web.csproj

@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+    <PropertyGroup>
+        <TargetFramework>net10.0</TargetFramework>
+        <Nullable>enable</Nullable>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <BlazorDisableThrowNavigationException>true</BlazorDisableThrowNavigationException>
+    </PropertyGroup>
+
+</Project>