Hide draft articles from the front page and mark drafts when viewed directly

Add an Article::published() scope and use it on the front page (which
previously showed drafts), the /blog listing and the feeds. Draft
articles are still reachable at their URL, but now show a draft notice,
a "[Draft]" title prefix and a noindex robots meta tag.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/Http/Controllers/FrontPageController.php

@@ -26,7 +26,7 @@ class FrontPageController extends Controller
             ->withCount(['webmentions AS reposts' => function ($query) {
                 $query->where('type', 'repost-of');
             }])->get();
-        $articles = Article::latest()->get();
+        $articles = Article::published()->latest()->get();
         $bookmarks = Bookmark::latest()->with('tags')->get();
         $likes = Like::latest()->get();