Style editor Markdown with .markdown-body and add ::: design blocks

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Elternbeirat.Web.Tests/PocketBaseFixture.cs

@@ -236,7 +236,11 @@ public sealed class PocketBaseFixture : IAsyncLifetime
         });
         await CreateRecordAsync(http, "pages", new
         {
-            title = "Förderverein", body = "# Förderverein", location = "header",
+            // The body uses a design block, so the smoke tests can follow a ":::"
+            // container through PocketBase and the page into the rendered HTML.
+            title = "Förderverein",
+            body = "Der Förderverein unterstützt die Schule.\n\n::: kennzahlen\n- **seit 1975** Gründung\n:::",
+            location = "header",
             order = 3, slug = "patrons", embed = Array.Empty<string>(), @public = true,
         });
         // Page record for the FAQ list. Route /faqs is served by FaqList, which reads