Own events domain templates (Phase 6)

Calendar, day, entry, slot, ticket templates + date macro moved
from shared to events/templates/. Cross-domain copies: post header,
post admin entries, cart mini.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

templates/macros/date.html

@@ -0,0 +1,7 @@
+{% macro dt(d) -%}
+{{ d.astimezone().strftime('%-d %b %Y, %H:%M') if d.tzinfo else d.strftime('%-d %b %Y, %H:%M') }}
+{%- endmacro %}
+
+{% macro t(d) -%}
+{{ d.astimezone().strftime('%H:%M') if d.tzinfo else d.strftime('%H:%M') }}
+{%- endmacro %}