Replace 21 Jinja render_template() calls with sx render functions

Phase 1: Wire 16 events routes to existing sx render functions
- slot, slots, ticket_types, ticket_type, calendar_entries,
  calendar_entry, calendar_entry/admin

Phase 2: Orders checkout return (2 calls)
- New orders/sx/checkout.sx with return page components
- New render_checkout_return_page() in orders/sx/sx_components.py

Phase 3: Blog menu items (3 calls)
- New blog/sx/menu_items.sx with search result components
- New render_menu_item_form() and render_page_search_results()
  in blog/sx/sx_components.py

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

events/bp/slots/routes.py

@@ -136,18 +136,13 @@ def register():
     @bp.get("/add")
     @require_admin
     async def add_form(**kwargs):
-        html = await render_template(
-            "_types/slots/_add.html",
-        )
-        return await make_response(html)
+        from sx.sx_components import render_slot_add_form
+        return sx_response(render_slot_add_form(g.calendar))
 
     @bp.get("/add-button")
     @require_admin
     async def add_button(**kwargs):
-        
-        html = await render_template(
-            "_types/slots/_add_button.html",
-        )
-        return await make_response(html)
+        from sx.sx_components import render_slot_add_button
+        return sx_response(render_slot_add_button(g.calendar))
 
     return bp