Add post and event cards, shared calendar sheet and per-event ICS; rework past events and next-event card

Elternbeirat.Web.Tests/PocketBaseClientTests.cs

@@ -17,8 +17,8 @@ public sealed class PocketBaseClientTests(PocketBaseFixture pocketBase)
 
         var events = await client.GetEventsAsync();
 
-        // Two seeded events, earliest start first.
-        events.Select(@event => @event.Title).ShouldBe(["Elternbeiratssitzung", "Herbstbasar"]);
+        // Three seeded events, earliest start first.
+        events.Select(@event => @event.Title).ShouldBe(["Projekttage", "Infoabend Klasse 5", "Elternbeiratssitzung", "Herbstbasar"]);
     }
 
     [Fact]