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/dashboard.sx

@@ -41,3 +41,20 @@
           name)
         logout)
       labels)))
+
+;; Assembled dashboard content — replaces Python _account_main_panel_sx
+(defcomp ~account-dashboard-content (&key error)
+  (let* ((user (current-user))
+         (csrf (csrf-token)))
+    (~account-main-panel
+      :error (when error (~account-error-banner :error error))
+      :email (when (get user "email")
+               (~account-user-email :email (get user "email")))
+      :name (when (get user "name")
+              (~account-user-name :name (get user "name")))
+      :logout (~account-logout-form :csrf-token csrf)
+      :labels (when (not (empty? (or (get user "labels") (list))))
+                (~account-labels-section
+                  :items (map (lambda (label)
+                    (~account-label-item :name (get label "name")))
+                    (get user "labels")))))))