Replace sx_call() with render_to_sx() across all services

Python no longer generates s-expression strings. All SX rendering now
goes through render_to_sx() which builds AST from native Python values
and evaluates via async_eval_to_sx() — no SX string literals in Python.

- Add render_to_sx()/render_to_html() infrastructure in shared/sx/helpers.py
- Add (abort status msg) IO primitive in shared/sx/primitives_io.py
- Convert all 9 services: ~650 sx_call() invocations replaced
- Convert shared helpers (root_header_sx, full_page_sx, etc.) to async
- Fix likes service import bug (likes.models → models)

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

market/bp/product/routes.py

@@ -129,7 +129,7 @@ def register():
       from sx.sx_components import render_like_toggle_button
 
       if not g.user:
-          return sx_response(render_like_toggle_button(product_slug, False), status=403)
+          return sx_response(await render_like_toggle_button(product_slug, False), status=403)
 
       user_id = g.user.id
 
@@ -138,7 +138,7 @@ def register():
       })
       liked = result["liked"]
 
-      return sx_response(render_like_toggle_button(product_slug, liked))
+      return sx_response(await render_like_toggle_button(product_slug, liked))
 
 
 
@@ -257,7 +257,7 @@ def register():
             from sx.sx_components import render_cart_added_response
             item_data = getattr(g, "item_data", {})
             d = item_data.get("d", {})
-            return sx_response(render_cart_added_response(g.cart, ci_ns, d))
+            return sx_response(await render_cart_added_response(g.cart, ci_ns, d))
 
         # normal POST: go to cart page
         from shared.infrastructure.urls import cart_url