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>

shared/infrastructure/activitypub.py

@@ -114,18 +114,18 @@ async def _render_profile_sx(actor, activities, total):
         # Import federation layout for OOB headers
         try:
             from federation.sxc.pages import _social_oob
-            oob_headers = _social_oob(tctx)
+            oob_headers = await _social_oob(tctx)
         except ImportError:
             oob_headers = ""
-        return sx_response(oob_page_sx(oobs=oob_headers, content=content))
+        return sx_response(await oob_page_sx(oobs=oob_headers, content=content))
     else:
         try:
             from federation.sxc.pages import _social_full
-            header_rows = _social_full(tctx)
+            header_rows = await _social_full(tctx)
         except ImportError:
             from shared.sx.helpers import root_header_sx
-            header_rows = root_header_sx(tctx)
-        return full_page_sx(tctx, header_rows=header_rows, content=content)
+            header_rows = await root_header_sx(tctx)
+        return await full_page_sx(tctx, header_rows=header_rows, content=content)
 
 
 def create_activitypub_blueprint(app_name: str) -> Blueprint: