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>
Move ~1670 lines to 6 sub-modules: renders.py, layouts.py, helpers.py,
cards.py, filters.py, utils.py. Update all bp route imports.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
