Extract date rendering into per-feature Date components

Elternbeirat.Web/Features/Events/EventDate.razor

@@ -0,0 +1,10 @@
+@*
+    Renders an event's date as a <time> element: the start in the machine-readable
+    datetime attribute, the full German range (weekday, clock time, multi-day span)
+    as visible text via EventDateFormat.
+
+    Unlike <PostDate>, this takes the whole Event, not a plain day: the visible
+    range depends on the event's end and whether it has a clock time, and that
+    logic already lives in EventDateFormat.
+*@
+<time datetime="@Value.Start.ToString("s")">@EventDateFormat.Range(Value)</time>