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/notifications.sx

@@ -20,3 +20,50 @@
 
 (defcomp ~federation-notifications-page (&key notifs)
   (h1 :class "text-2xl font-bold mb-6" "Notifications") notifs)
+
+;; Assembled notification card — replaces Python _notification_sx
+(defcomp ~federation-notification-from-data (&key notif)
+  (let* ((from-name (or (get notif "from_actor_name") "?"))
+         (from-username (or (get notif "from_actor_username") ""))
+         (from-domain (or (get notif "from_actor_domain") ""))
+         (from-icon (get notif "from_actor_icon"))
+         (ntype (or (get notif "notification_type") ""))
+         (preview (get notif "target_content_preview"))
+         (created (or (get notif "created_at_formatted") ""))
+         (read (get notif "read"))
+         (app-domain (or (get notif "app_domain") ""))
+         (border (if (not read) " border-l-4 border-l-stone-400" ""))
+         (initial (if (and (not from-icon) from-name)
+                    (upper (slice from-name 0 1)) "?"))
+         (action-text (cond
+           ((= ntype "follow") (str "followed you"
+             (if (and app-domain (!= app-domain "federation"))
+               (str " on " (escape app-domain)) "")))
+           ((= ntype "like") "liked your post")
+           ((= ntype "boost") "boosted your post")
+           ((= ntype "mention") "mentioned you")
+           ((= ntype "reply") "replied to your post")
+           (true ""))))
+    (~federation-notification-card
+      :cls (str "bg-white rounded-lg shadow-sm border border-stone-200 p-4" border)
+      :avatar (~avatar
+        :src from-icon
+        :cls (if from-icon "w-8 h-8 rounded-full"
+               "w-8 h-8 rounded-full bg-stone-300 flex items-center justify-center text-stone-600 font-bold text-xs")
+        :initial (when (not from-icon) initial))
+      :from-name (escape from-name)
+      :from-username (escape from-username)
+      :from-domain (if from-domain (str "@" (escape from-domain)) "")
+      :action-text action-text
+      :preview (when preview (~federation-notification-preview :preview (escape preview)))
+      :time created)))
+
+;; Assembled notifications content — replaces Python _notifications_content_sx
+(defcomp ~federation-notifications-content (&key notifications)
+  (~federation-notifications-page
+    :notifs (if (empty? notifications)
+      (~empty-state :message "No notifications yet." :cls "text-stone-500")
+      (~federation-notifications-list
+        :items (map (lambda (n)
+          (~federation-notification-from-data :notif n))
+          notifications)))))