refactor(theme): extract home-predeparture partial; trip-feed-col single-purpose

Addresses code-review finding: the pre_departure branch made trip-feed-col
dual-purpose. Pre-departure landing now lives in its own partial; home picks
it via {% if all_items|length == 0 %}, and trip-feed-col drops the
pre_departure param to be shared 1:1 by both callers.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BftDn9vu9SonFAY4vxu4uk

themes/intotheeast/templates/trip.html.twig

@@ -76,8 +76,7 @@
         has_gpx: has_gpx,
         gpx_urls: gpx_urls,
         gps_points: gps_points,
-        show_sort: true,
-        pre_departure: false
+        show_sort: true
     } only %}
 </div>