Remove render_to_sx from public API: enforce sx_call for all service code

Replace ~250 render_to_sx calls across all services with sync sx_call,
converting many async functions to sync where no other awaits remained.
Make render_to_sx/render_to_sx_with_env private (_render_to_sx).
Add (post-header-ctx) IO primitive and shared post/post-admin defmacros.
Convert built-in post/post-admin layouts from Python to register_sx_layout
with .sx defcomps. Remove dead post_admin_mobile_nav_sx.

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

events/sxc/pages/utils.py

@@ -1,7 +1,7 @@
 """Badge helpers, OOB helpers, formatting utilities, list containers."""
 from __future__ import annotations
 
-from shared.sx.helpers import render_to_sx
+from shared.sx.helpers import sx_call
 from shared.sx.parser import SxExpr
 
 
@@ -74,7 +74,7 @@ def _list_container(ctx: dict) -> str:
     return getattr(styles, "list_container", "") if hasattr(styles, "list_container") else styles.get("list_container", "")
 
 
-async def _entry_state_badge_html(state: str) -> str:
+def _entry_state_badge_html(state: str) -> str:
     """Render an entry state badge."""
     state_classes = {
         "confirmed": "bg-emerald-100 text-emerald-800",
@@ -85,10 +85,10 @@ async def _entry_state_badge_html(state: str) -> str:
     }
     cls = state_classes.get(state, "bg-stone-100 text-stone-700")
     label = state.replace("_", " ").capitalize()
-    return await render_to_sx("badge", cls=cls, label=label)
+    return sx_call("badge", cls=cls, label=label)
 
 
-async def _ticket_state_badge_html(state: str) -> str:
+def _ticket_state_badge_html(state: str) -> str:
     """Render a ticket state badge."""
     cls_map = {
         "confirmed": "bg-emerald-100 text-emerald-800",
@@ -98,7 +98,7 @@ async def _ticket_state_badge_html(state: str) -> str:
     }
     cls = cls_map.get(state, "bg-stone-100 text-stone-700")
     label = (state or "").replace("_", " ").capitalize()
-    return await render_to_sx("badge", cls=cls, label=label)
+    return sx_call("badge", cls=cls, label=label)
 
 
 # ---------------------------------------------------------------------------
@@ -109,21 +109,21 @@ _LIST_SVG = None
 _TILE_SVG = None
 
 
-async def _get_list_svg():
+def _get_list_svg():
     global _LIST_SVG
     if _LIST_SVG is None:
-        _LIST_SVG = await render_to_sx("list-svg")
+        _LIST_SVG = sx_call("list-svg")
     return _LIST_SVG
 
 
-async def _get_tile_svg():
+def _get_tile_svg():
     global _TILE_SVG
     if _TILE_SVG is None:
-        _TILE_SVG = await render_to_sx("tile-svg")
+        _TILE_SVG = sx_call("tile-svg")
     return _TILE_SVG
 
 
-async def _view_toggle_html(ctx: dict, view: str) -> str:
+def _view_toggle_html(ctx: dict, view: str) -> str:
     """Render the list/tile view toggle bar."""
     from shared.utils import route_prefix
     prefix = route_prefix()
@@ -142,14 +142,14 @@ async def _view_toggle_html(ctx: dict, view: str) -> str:
     list_active = 'bg-stone-200 text-stone-800' if view != 'tile' else 'text-stone-400 hover:text-stone-600'
     tile_active = 'bg-stone-200 text-stone-800' if view == 'tile' else 'text-stone-400 hover:text-stone-600'
 
-    return await render_to_sx("view-toggle",
+    return sx_call("view-toggle",
                   list_href=list_href, tile_href=tile_href,
                   hx_select=hx_select, list_cls=list_active,
                   tile_cls=tile_active, storage_key="events_view",
-                  list_svg=SxExpr(await _get_list_svg()), tile_svg=SxExpr(await _get_tile_svg()))
+                  list_svg=SxExpr(_get_list_svg()), tile_svg=SxExpr(_get_tile_svg()))
 
 
-async def _cart_icon_oob(count: int) -> str:
+def _cart_icon_oob(count: int) -> str:
     """Render the OOB cart icon/badge swap."""
     from quart import g
 
@@ -163,9 +163,9 @@ async def _cart_icon_oob(count: int) -> str:
 
     if count == 0:
         blog_href = blog_url_fn("/") if blog_url_fn else "/"
-        return await render_to_sx("events-cart-icon-logo",
+        return sx_call("events-cart-icon-logo",
                       blog_href=blog_href, logo=logo)
 
     cart_href = cart_url_fn("/") if cart_url_fn else "/"
-    return await render_to_sx("events-cart-icon-badge",
+    return sx_call("events-cart-icon-badge",
                   cart_href=cart_href, count=str(count))