Implement P1 local matcher/ledger and P2 strategy engine.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/sim/__init__.py

@@ -1 +1,15 @@
-# Placeholder packages for later phases (P1–P5).
+from .ledger import Ledger
+from .liquidity import bid_covers_eth, contracts_for_eth
+from .matcher import CloseResult, Matcher, OpenResult
+from .pricing import option_fill, perp_fill
+
+__all__ = [
+    "CloseResult",
+    "Ledger",
+    "Matcher",
+    "OpenResult",
+    "bid_covers_eth",
+    "contracts_for_eth",
+    "option_fill",
+    "perp_fill",
+]