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>

blog/sx/index.sx

@@ -1,55 +1,8 @@
 ;; Blog index components
 
-(defcomp ~blog-end-of-results ()
-  (div :class "col-span-full mt-4 text-center text-xs text-stone-400" "End of results"))
-
-(defcomp ~blog-sentinel-mobile (&key id next-url hyperscript)
-  (div :id id :class "block md:hidden h-[60vh] opacity-0 pointer-events-none js-mobile-sentinel"
-    :sx-get next-url :sx-trigger "intersect once delay:250ms, sentinelmobile:retry"
-    :sx-swap "outerHTML" :_ hyperscript
-    :role "status" :aria-live "polite" :aria-hidden "true"
-    (div :class "js-loading hidden flex justify-center py-8"
-      (div :class "animate-spin h-8 w-8 border-4 border-stone-300 border-t-stone-600 rounded-full"))
-    (div :class "js-neterr hidden text-center py-8 text-stone-400"
-      (i :class "fa fa-exclamation-triangle text-2xl")
-      (p :class "mt-2" "Loading failed \u2014 retrying\u2026"))))
-
-(defcomp ~blog-sentinel-desktop (&key id next-url hyperscript)
-  (div :id id :class "hidden md:block h-4 opacity-0 pointer-events-none"
-    :sx-get next-url :sx-trigger "intersect once delay:250ms, sentinel:retry"
-    :sx-swap "outerHTML" :_ hyperscript
-    :role "status" :aria-live "polite" :aria-hidden "true"
-    (div :class "js-loading hidden flex justify-center py-2"
-      (div :class "animate-spin h-6 w-6 border-2 border-stone-300 border-t-stone-600 rounded-full"))
-    (div :class "js-neterr hidden text-center py-2 text-stone-400 text-sm" "Retry\u2026")))
-
-(defcomp ~blog-page-sentinel (&key id next-url)
-  (div :id id :class "h-4 opacity-0 pointer-events-none"
-    :sx-get next-url :sx-trigger "intersect once delay:250ms" :sx-swap "outerHTML"))
-
 (defcomp ~blog-no-pages ()
   (div :class "col-span-full mt-8 text-center text-stone-500" "No pages found."))
 
-(defcomp ~blog-list-svg ()
-  (svg :xmlns "http://www.w3.org/2000/svg" :class "h-5 w-5" :fill "none" :viewBox "0 0 24 24"
-    :stroke "currentColor" :stroke-width "2"
-    (path :stroke-linecap "round" :stroke-linejoin "round" :d "M4 6h16M4 12h16M4 18h16")))
-
-(defcomp ~blog-tile-svg ()
-  (svg :xmlns "http://www.w3.org/2000/svg" :class "h-5 w-5" :fill "none" :viewBox "0 0 24 24"
-    :stroke "currentColor" :stroke-width "2"
-    (path :stroke-linecap "round" :stroke-linejoin "round"
-      :d "M4 5a1 1 0 011-1h4a1 1 0 011 1v4a1 1 0 01-1 1H5a1 1 0 01-1-1V5zM14 5a1 1 0 011-1h4a1 1 0 011 1v4a1 1 0 01-1 1h-4a1 1 0 01-1-1V5zM4 15a1 1 0 011-1h4a1 1 0 011 1v4a1 1 0 01-1 1H5a1 1 0 01-1-1v-4zM14 15a1 1 0 011-1h4a1 1 0 011 1v4a1 1 0 01-1 1h-4a1 1 0 01-1-1v-4z")))
-
-(defcomp ~blog-view-toggle (&key list-href tile-href hx-select list-cls tile-cls list-svg tile-svg)
-  (div :class "hidden md:flex justify-end px-3 pt-3 gap-1"
-    (a :href list-href :sx-get list-href :sx-target "#main-panel" :sx-select hx-select
-      :sx-swap "outerHTML" :sx-push-url "true" :class (str "p-1.5 rounded " list-cls) :title "List view"
-      :_ "on click js localStorage.removeItem('blog_view') end" list-svg)
-    (a :href tile-href :sx-get tile-href :sx-target "#main-panel" :sx-select hx-select
-      :sx-swap "outerHTML" :sx-push-url "true" :class (str "p-1.5 rounded " tile-cls) :title "Tile view"
-      :_ "on click js localStorage.setItem('blog_view','tile') end" tile-svg)))
-
 (defcomp ~blog-content-type-tabs (&key posts-href pages-href hx-select posts-cls pages-cls)
   (div :class "flex justify-center gap-1 px-3 pt-3"
     (a :href posts-href :sx-get posts-href :sx-target "#main-panel"