Centre one 42rem reading column on content, post, event and FAQ pages

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

@@ -1,13 +1,21 @@
-/* The article: a reading column of about 68 characters with generous leading, so a
-   long post reads like a page, not like a form. Everything inside follows this
-   width -- the global 42rem cap on paragraphs, lists and boxes is lifted here, or
-   the text would stop short of the column it sits in. */
+/* The article: the site's centred 42rem reading column (as on a content page,
+   ContentPage.razor.css) with generous leading, so a long post reads like a page,
+   not like a form. Everything inside follows this width -- the global 42rem cap on
+   paragraphs, lists and boxes is lifted here, so nothing stops short of the column
+   (the post's own leading makes the text a touch wider than elsewhere). */
 .post {
-    max-width: 68ch;
-    margin-top: var(--space-4);
+    max-width: 42rem;
+    margin: var(--space-4) auto 0;
     line-height: 1.75;
 }
 
+/* The back link is an inline button, which margin: auto cannot centre. A left
+   margin of half the free space puts it on the column's left edge instead, and
+   max() keeps it at 0 once the screen is narrower than the column. */
+.btn-quiet {
+    margin-left: max(0px, (100% - 42rem) / 2);
+}
+
 .post ::deep :is(p, ul, ol, blockquote, .aufruf, .hinweis) {
     max-width: none;
 }
@@ -46,8 +54,8 @@
     display: grid;
     grid-template-columns: 1fr 1fr;
     gap: var(--space-3);
-    max-width: 68ch;
-    margin-top: var(--space-6);
+    max-width: 42rem;
+    margin: var(--space-6) auto 0;
     padding-top: var(--space-4);
     border-top: 1px solid var(--color-border);
 }