Move SX construction from Python to .sx defcomps (phases 0-4)

Eliminate Python s-expression string building across account, orders,
federation, and cart services. Visual rendering logic now lives entirely
in .sx defcomp components; Python files contain only data serialization,
header/layout wiring, and thin wrappers that call defcomps.

Phase 0: Shared DRY extraction — auth/orders header defcomps, format-decimal/
pluralize/escape/route-prefix primitives.
Phase 1: Account — dashboard, newsletters, login/device/check-email content.
Phase 2: Orders — order list, detail, filter, checkout return assembled defcomps.
Phase 3: Federation — social nav, post cards, timeline, search, actors,
notifications, compose, profile assembled defcomps.
Phase 4: Cart — overview, page cart items/calendar/tickets/summary, admin,
payments assembled defcomps; orders rendering reuses Phase 2 shared defcomps.

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

account/sx/newsletters.sx

@@ -29,3 +29,34 @@
     (div :class "bg-white/70 backdrop-blur rounded-2xl shadow border border-stone-200 p-6 sm:p-8 space-y-6"
       (h1 :class "text-xl font-semibold tracking-tight" "Newsletters")
       list)))
+
+;; Assembled newsletters content — replaces Python _newsletters_panel_sx
+;; Takes pre-fetched newsletter-list from page helper
+(defcomp ~account-newsletters-content (&key newsletter-list account-url)
+  (let* ((csrf (csrf-token)))
+    (if (empty? newsletter-list)
+      (~account-newsletter-empty)
+      (~account-newsletters-panel
+        :list (~account-newsletter-list
+          :items (map (lambda (item)
+            (let* ((nl (get item "newsletter"))
+                   (un (get item "un"))
+                   (nid (get nl "id"))
+                   (subscribed (get item "subscribed"))
+                   (toggle-url (str (or account-url "") "/newsletter/" nid "/toggle/"))
+                   (bg (if subscribed "bg-emerald-500" "bg-stone-300"))
+                   (translate (if subscribed "translate-x-6" "translate-x-1"))
+                   (checked (if subscribed "true" "false")))
+              (~account-newsletter-item
+                :name (get nl "name")
+                :desc (when (get nl "description")
+                        (~account-newsletter-desc :description (get nl "description")))
+                :toggle (~account-newsletter-toggle
+                  :id (str "nl-" nid)
+                  :url toggle-url
+                  :hdrs (str "{\"X-CSRFToken\": \"" csrf "\"}")
+                  :target (str "#nl-" nid)
+                  :cls (str "relative inline-flex h-6 w-11 items-center rounded-full transition-colors focus:outline-none focus:ring-2 focus:ring-emerald-500 focus:ring-offset-2 " bg)
+                  :checked checked
+                  :knob-cls (str "inline-block h-4 w-4 rounded-full bg-white shadow transform transition-transform " translate)))))
+            newsletter-list))))))