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>

federation/sx/profile.sx

@@ -53,3 +53,40 @@
 
 (defcomp ~federation-profile-summary-text (&key text)
   (p :class "mt-2" text))
+
+;; Assembled actor timeline content — replaces Python _actor_timeline_content_sx
+(defcomp ~federation-actor-timeline-content (&key remote-actor items is-following actor)
+  (let* ((display-name (or (get remote-actor "display_name") (get remote-actor "preferred_username") ""))
+         (icon-url (get remote-actor "icon_url"))
+         (summary (get remote-actor "summary"))
+         (actor-url (or (get remote-actor "actor_url") ""))
+         (csrf (csrf-token))
+         (initial (if (and (not icon-url) display-name)
+                    (upper (slice display-name 0 1)) "?")))
+    (~federation-actor-timeline-layout
+      :header (~federation-actor-profile-header
+        :avatar (~avatar
+          :src icon-url
+          :cls (if icon-url "w-16 h-16 rounded-full"
+                 "w-16 h-16 rounded-full bg-stone-300 flex items-center justify-center text-stone-600 font-bold text-xl")
+          :initial (when (not icon-url) initial))
+        :display-name (escape display-name)
+        :username (escape (or (get remote-actor "preferred_username") ""))
+        :domain (escape (or (get remote-actor "domain") ""))
+        :summary (when summary (~federation-profile-summary :summary summary))
+        :follow (when actor
+          (if is-following
+            (~federation-follow-form
+              :action (url-for "social.unfollow") :csrf csrf :actor-url actor-url
+              :label "Unfollow"
+              :cls "border border-stone-300 rounded px-4 py-2 hover:bg-stone-100")
+            (~federation-follow-form
+              :action (url-for "social.follow") :csrf csrf :actor-url actor-url
+              :label "Follow"
+              :cls "bg-stone-800 text-white rounded px-4 py-2 hover:bg-stone-700"))))
+      :timeline (~federation-timeline-items
+        :items items :timeline-type "actor" :actor actor
+        :next-url (when (not (empty? items))
+          (url-for "social.actor_timeline_page"
+                   :id (get remote-actor "id")
+                   :before (get (last items) "before_cursor")))))))