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>

events/bp/ticket_admin/routes.py

@@ -54,7 +54,7 @@ def register() -> Blueprint:
         tickets = await get_tickets_for_entry(g.s, entry_id)
 
         from sx.sx_components import render_entry_tickets_admin
-        html = render_entry_tickets_admin(entry, tickets)
+        html = await render_entry_tickets_admin(entry, tickets)
         return sx_response(html)
 
     @bp.get("/lookup/")
@@ -71,9 +71,9 @@ def register() -> Blueprint:
         ticket = await get_ticket_by_code(g.s, code)
         from sx.sx_components import render_lookup_result
         if not ticket:
-            return sx_response(render_lookup_result(None, "Ticket not found"))
+            return sx_response(await render_lookup_result(None, "Ticket not found"))
 
-        return sx_response(render_lookup_result(ticket, None))
+        return sx_response(await render_lookup_result(ticket, None))
 
     @bp.post("/<code>/checkin/")
     @require_admin
@@ -84,9 +84,9 @@ def register() -> Blueprint:
 
         from sx.sx_components import render_checkin_result
         if not success:
-            return sx_response(render_checkin_result(False, error, None))
+            return sx_response(await render_checkin_result(False, error, None))
 
         ticket = await get_ticket_by_code(g.s, code)
-        return sx_response(render_checkin_result(True, None, ticket))
+        return sx_response(await render_checkin_result(True, None, ticket))
 
     return bp