Fix events: use cart-mini fragment instead of local cart template

Events was trying to render _types/cart/_mini.html locally, which only
exists in the cart service. Replace with fetch_fragment("cart", "cart-mini")
calls and add oob param support to the cart-mini fragment.

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

cart/bp/fragments/routes.py

@@ -32,7 +32,8 @@ def register():
             g.s, user_id=user_id, session_id=session_id,
         )
         count = summary.count + summary.calendar_count + summary.ticket_count
-        return await render_template("fragments/cart_mini.html", cart_count=count)
+        oob = request.args.get("oob", "")
+        return await render_template("fragments/cart_mini.html", cart_count=count, oob=oob)
 
     async def _account_nav_item():
         from shared.infrastructure.urls import cart_url

cart/templates/fragments/cart_mini.html

@@ -1,4 +1,4 @@
-<div id="cart-mini">
+<div id="cart-mini" {% if oob %}hx-swap-oob="true"{% endif %}>
   {% if cart_count == 0 %}
   <div class="h-12 w-12 rounded-full overflow-hidden border border-stone-300 flex-shrink-0">
     <a