Extract date rendering into per-feature Date components

Elternbeirat.Web/Features/Posts/PostDate.razor.css

@@ -0,0 +1,9 @@
+/* The date's own look: small and softened. Lives with the component so every
+   place that renders <PostDate> (list, home embed, detail page) shows the date
+   the same way. Positioning (margin to neighbours) is NOT set here -- that
+   depends on the surrounding context and is set by each caller. */
+time {
+    display: block;
+    color: var(--color-text-soft);   /* token, so it adapts in dark mode */
+    font-size: 0.85rem;
+}