Add home hero with intro and buttons from the body, next-event card and page tiles

Elternbeirat.Web.Tests/FixedTimeProvider.cs

@@ -0,0 +1,13 @@
+namespace Elternbeirat.Web.Tests;
+
+/// <summary>
+/// A clock that always shows the same moment, so tests can decide what "today" is
+/// (e.g. before or after the fixture's events). Hand-written instead of
+/// Microsoft.Extensions.TimeProvider.Testing: overriding one method does not justify
+/// a new package.
+/// </summary>
+/// <param name="now">The moment the clock shows.</param>
+internal sealed class FixedTimeProvider(DateTimeOffset now) : TimeProvider
+{
+    public override DateTimeOffset GetUtcNow() => now;
+}