Move events/market/blog composition from Python to .sx defcomps (Phase 9)

Continues the pattern of eliminating Python sx_call tree-building in favour
of data-driven .sx defcomps. POST/PUT/DELETE routes now pass plain data
(dicts, lists, scalars) and let .sx handle iteration, conditionals, and
layout via map/let/when/if. Single response components wrap OOB swaps.

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

market/sxc/pages/cards.py

@@ -197,12 +197,6 @@ def _market_cards_sx(markets: list, page_info: dict, page: int, has_more: bool,
                    next_url=next_url)
 
 
-def _markets_grid(cards_sx: str) -> str:
-    """Wrap market cards in a grid as sx."""
-    from shared.sx.parser import SxExpr
-    return sx_call("market-markets-grid", cards=SxExpr(cards_sx))
-
-
 def _no_markets_sx(message: str = "No markets available") -> str:
     """Empty state for markets as sx."""
     return sx_call("empty-state", icon="fa fa-store", message=message,