Delete account/sx/sx_components.py — all rendering now in .sx

Phase 1 of zero-Python rendering: account service.

- Auth pages (login, device, check-email) use _render_auth_page() helper
  calling render_to_sx() + full_page_sx() directly in routes
- Newsletter toggle POST renders inline via render_to_sx()
- Newsletter page helper returns data dict; defpage :data slot fetches,
  :content slot renders via ~account-newsletters-content defcomp
- Fragment page uses (frag ...) IO primitive directly in .sx
- Defpage _eval_slot now uses async_eval_slot_to_sx which expands
  component bodies server-side (executing IO) but serializes tags as SX
- Fix pre-existing OOB ParseError: _eval_slot was producing HTML instead
  of s-expressions for component content slots
- Fix market url_for endpoint: defpage_market_home (app-level, not blueprint)
- Fix events calendar nav: wrap multiple SX parts in fragment

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

events/sx/sx_components.py

@@ -198,7 +198,7 @@ async def _calendar_nav_sx(ctx: dict) -> str:
         admin_href = url_for("defpage_calendar_admin", calendar_slug=cal_slug)
         parts.append(await render_to_sx("nav-link", href=admin_href, icon="fa fa-cog",
                             select_colours=select_colours))
-    return "".join(parts)
+    return "(<> " + " ".join(parts) + ")" if parts else ""
 
 
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