Refactor SX templates: shared components, Python migration, cleanup

- Extract shared components (empty-state, delete-btn, sentinel, crud-*,
  view-toggle, img-or-placeholder, avatar, sumup-settings-form, auth
  forms, order tables/detail/checkout)
- Migrate all Python sx_call() callers to use shared components directly
- Remove 55+ thin wrapper defcomps from domain .sx files
- Remove trivial passthrough wrappers (blog-header-label, market-card-text, etc)
- Unify duplicate auth flows (account + federation) into shared/sx/templates/auth.sx
- Unify duplicate order views (cart + orders) into shared/sx/templates/orders.sx
- Disable static file caching in dev (SEND_FILE_MAX_AGE_DEFAULT=0)
- Add SX response validation and debug headers

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

events/sx/calendar.sx

@@ -36,45 +36,6 @@
       (div :class "hidden sm:grid grid-cols-7 text-center text-md font-semibold text-stone-700 mb-2" weekdays)
       (div :class "grid grid-cols-1 sm:grid-cols-7 gap-px bg-stone-200 rounded-xl overflow-hidden" cells))))
 
-(defcomp ~events-calendars-create-form (&key create-url csrf)
-  (<>
-    (div :id "cal-create-errors" :class "mt-2 text-sm text-red-600")
-    (form :class "mt-4 flex gap-2 items-end" :sx-post create-url
-          :sx-target "#calendars-list" :sx-select "#calendars-list" :sx-swap "outerHTML"
-          :sx-on:beforeRequest "document.querySelector('#cal-create-errors').textContent='';"
-          :sx-on:responseError "document.querySelector('#cal-create-errors').textContent='Error'; if(event.detail.response){event.detail.response.clone().text().then(function(t){event.target.closest('form').querySelector('[id$=errors]').innerHTML=t})}"
-      (input :type "hidden" :name "csrf_token" :value csrf)
-      (div :class "flex-1"
-        (label :class "block text-sm text-gray-600" "Name")
-        (input :name "name" :type "text" :required true :class "w-full border rounded px-3 py-2"
-               :placeholder "e.g. Events, Gigs, Meetings"))
-      (button :type "submit" :class "border rounded px-3 py-2" "Add calendar"))))
-
-(defcomp ~events-calendars-panel (&key form list)
-  (section :class "p-4"
-    form
-    (div :id "calendars-list" :class "mt-6" list)))
-
-(defcomp ~events-calendars-empty ()
-  (p :class "text-gray-500 mt-4" "No calendars yet. Create one above."))
-
-(defcomp ~events-calendars-item (&key href cal-name cal-slug del-url csrf-hdr)
-  (div :class "mt-6 border rounded-lg p-4"
-    (div :class "flex items-center justify-between gap-3"
-      (a :class "flex items-baseline gap-3" :href href
-         :sx-get href :sx-target "#main-panel" :sx-select "#main-panel" :sx-swap "outerHTML" :sx-push-url "true"
-        (h3 :class "font-semibold" cal-name)
-        (h4 :class "text-gray-500" (str "/" cal-slug "/")))
-      (button :class "text-sm border rounded px-3 py-1 hover:bg-red-50 hover:border-red-400"
-              :data-confirm true :data-confirm-title "Delete calendar?"
-              :data-confirm-text "Entries will be hidden (soft delete)"
-              :data-confirm-icon "warning" :data-confirm-confirm-text "Yes, delete it"
-              :data-confirm-cancel-text "Cancel" :data-confirm-event "confirmed"
-              :sx-delete del-url :sx-trigger "confirmed"
-              :sx-target "#calendars-list" :sx-select "#calendars-list" :sx-swap "outerHTML"
-              :sx-headers csrf-hdr
-        (i :class "fa-solid fa-trash")))))
-
 (defcomp ~events-calendar-description-display (&key description edit-url)
   (div :id "calendar-description"
     (if description