Read a post's date as the Berlin calendar day, not the raw UTC day

Elternbeirat.Contracts/Post.cs

@@ -1,3 +1,4 @@
+using System.ComponentModel;
 using System.Text.Json.Serialization;
 
 namespace Elternbeirat.Contracts;
@@ -17,14 +18,16 @@ public record Post
     public string Id { get; init; } = "";
 
     /// <summary>
-    ///     Gets the publication date as Europe/Berlin wall-clock time.
+    ///     Gets the publication date as a calendar day.
     /// </summary>
     /// <remarks>
-    ///     PocketBase stores the value in UTC; it is converted to Berlin local time on
-    ///     deserialization, with daylight saving applied. Only the date part is shown.
+    ///     A post's date is a plain day, not a point in time. It is read as the
+    ///     Berlin calendar day: the UTC value is converted to Europe/Berlin and only
+    ///     the day is kept, so the day an editor picked is the day shown -- no
+    ///     time-of-day, no off-by-one at midnight. See <see cref="DateOnlyConverter"/>.
     /// </remarks>
     [JsonPropertyName("date")]
-    public DateTime Date { get; init; }
+    public DateOnly Date { get; init; }
 
     /// <summary>
     ///     Gets the heading shown to visitors.