Serve 503 when PocketBase is unavailable across all content pages

Elternbeirat.Web/Features/Posts/PostDetail.razor

@@ -1,19 +1,25 @@
 @page "/posts/{Slug}"
 
-@if (_post is null)
+@if (_unavailable)
 {
-    <PageTitle>Nicht gefunden</PageTitle>
+    <PageTitle>Vorübergehend nicht erreichbar</PageTitle>
+    <p>Der Beitrag ist gerade nicht erreichbar. Bitte später erneut versuchen.</p>
 }
-else
+else if (_post is not null)
 {
     <PageTitle>@_post.Title</PageTitle>
+    <nav>
+        <a href="/posts">&larr; Alle Beiträge</a>
+    </nav>
     <article>
-        <p class="post-meta">
-            <a href="/posts">&larr; Alle Beiträge</a>
-            <time datetime="@_post.Date.ToString("yyyy-MM-dd")">
-                @_post.Date.ToString("d. MMMM yyyy", German)
+        <header>
+            <h1>@_post.Title</h1>
+            <time class="post-meta" datetime="@_post.Date.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture)">
+                @_post.Date.ToString("d. MMMM yyyy", Cultures.German)
             </time>
-        </p>
+        </header>
         @Body
     </article>
 }
+@* No post and not unavailable: the slug was unknown; NavigationManager.NotFound()
+   already ran in OnParametersSetAsync and renders the not-found page. *@