feat: add filter bar markup and pill button styles to trip page

Replace the old trip-nav links with a new filter bar component featuring:
- Three pill buttons for filtering (All content, Journal, Stories)
- "All content" button active by default with teal accent styling
- Separate Stats button with matching pill styling
- CSS for buttons with hover and active states
- Responsive flexbox layout that wraps on narrow screens

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

themes/intotheeast/templates/trip.html.twig

@@ -55,11 +55,14 @@
                 {{ journal_count }} journal {{ journal_count == 1 ? 'entry' : 'entries' }}
                 {% if story_count > 0 %} · {{ story_count }} {{ story_count == 1 ? 'story' : 'stories' }}{% endif %}
             </span>
-            <nav class="trip-nav">
-                <a href="{{ page.route }}/dailies">Journal</a>
-                <a href="{{ page.route }}/stats">Stats</a>
-                <a href="{{ page.route }}/stories">Stories</a>
-            </nav>
+            <div class="trip-filter-bar">
+                <div class="trip-filter-group">
+                    <button class="trip-filter-btn is-active" data-filter="all">All content</button>
+                    <button class="trip-filter-btn" data-filter="journal">Journal</button>
+                    <button class="trip-filter-btn" data-filter="story">Stories</button>
+                </div>
+                <button class="trip-stats-btn" id="trip-stats-toggle">Stats</button>
+            </div>
         </div>
 
         <div class="feed">