fix: make page title <h1> conditional to prevent double headings (v1.0.3)

When plugins inject content via TwigService with empty post.title,
the theme's <h1> is now skipped. Prevents duplicate headings on
plugin-rendered pages that provide their own titles.

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

views/pages/page.html.twig

@@ -10,7 +10,9 @@
             </figure>
         {% endif %}
 
-        <h1>{{ post.title }}</h1>
+        {% if post.title is not empty %}
+            <h1>{{ post.title }}</h1>
+        {% endif %}
 
         <div class="post-content">
             {{ post.content|raw }}