fix(story): add end_date blueprint field; fix date range display

Blueprint: renamed 'Date' to 'Start Date', added optional 'End Date'
field (header.end_date) so it's editable in Admin.

Template: single date → 'd M Y'; range → 'd M Y – d M Y' (full year
on both sides — the old format silently dropped the start year).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Vgmzx8VTTTmCskSpQtsLTr

themes/intotheeast/templates/story.html.twig

@@ -13,8 +13,7 @@
 
 {% set date_str = page.date|date('d M Y') %}
 {% if page.header.end_date %}
-    {% set end_str = page.header.end_date|date('d M Y') %}
-    {% set date_str = page.date|date('d M') ~ '–' ~ end_str %}
+    {% set date_str = page.date|date('d M Y') ~ ' – ' ~ page.header.end_date|date('d M Y') %}
 {% endif %}
 
 {% set location = page.header.location_name ?? '' %}