fix: address PR #574 fourth review round

- Use lowercase generics (list[...]) in new deck response models
- Add clarifying comment on AddressBook.uri slug semantics
- Fall back calendar_display_name to calendar_name when absent

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

nextcloud_mcp_server/server/calendar.py

@@ -44,7 +44,8 @@ def _event_dict_to_summary(event: dict) -> CalendarEventSummary:
         categories=categories,
         status=event.get("status"),
         calendar_name=event.get("calendar_name"),
-        calendar_display_name=event.get("calendar_display_name"),
+        calendar_display_name=event.get("calendar_display_name")
+        or event.get("calendar_name"),
     )