Fix DTO compatibility in cart templates and page_cart service

- page_cart.py: use ce.calendar_container_id instead of ce.calendar.container_id
- _cart.html: use entry.calendar_name instead of entry.calendar.name
- Update shared submodule with DTO field additions

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

bp/cart/services/page_cart.py

@@ -101,8 +101,8 @@ async def get_cart_grouped_by_page(session) -> list[dict]:
         groups[pid]["cart_items"].append(ci)
 
     for ce in cal_entries:
-        if ce.calendar and ce.calendar.container_id:
-            pid = ce.calendar.container_id
+        if ce.calendar_container_id:
+            pid = ce.calendar_container_id
         else:
             pid = None
         groups[pid]["post_id"] = pid

templates/_types/cart/_cart.html

@@ -43,7 +43,7 @@
                 <li class="flex items-start justify-between text-sm">
                   <div>
                     <div class="font-medium">
-                      {{ entry.name or entry.calendar.name }}
+                      {{ entry.name or entry.calendar_name }}
                     </div>
                     <div class="text-xs text-stone-500">
                       {{ entry.start_at }}