fix: nav slash, back button context, home page max-width

- Past Trips nav link: add missing / (base_url_absolute has no trailing slash)
- Entry back link: history.back() with journal fallback, label → "← Back"
- Home page: max-width 1400px instead of none — narrows layout on wide screens

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RB86BaJBG3eGiMdfhmHRrQ

themes/intotheeast/templates/entry.html.twig

@@ -121,7 +121,7 @@
     {% endif %}
 
     <footer class="entry-footer">
-        <a href="{{ page.parent().url }}">← Back to journal</a>
+        <a href="{{ page.parent().url }}" onclick="if(history.length>1){event.preventDefault();history.back()}">← Back</a>
     </footer>
 </article>
 {% endblock %}