Implement P1 local matcher/ledger and P2 strategy engine.

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

backend/app/sim/ledger.py

@@ -0,0 +1,61 @@
+from __future__ import annotations
+
+import time
+from typing import Any
+
+from ..models.db import Database, get_db
+
+
+class Ledger:
+    def __init__(self, db: Database | None = None) -> None:
+        self.db = db or get_db()
+
+    def snapshot(self) -> dict[str, Any]:
+        row = self.db.fetchone("SELECT * FROM ledger_meta WHERE id=1")
+        assert row is not None
+        return {
+            "equity": float(row["equity"]),
+            "available": float(row["available"]),
+            "reserved": float(row["reserved"]),
+            "updated_at_ms": int(row["updated_at_ms"]),
+        }
+
+    def apply_cash(
+        self,
+        amount: float,
+        *,
+        kind: str,
+        group_id: str | None = None,
+        note: str = "",
+    ) -> float:
+        """amount>0 入账；amount<0 出账。返回余额。"""
+        now = int(time.time() * 1000)
+        with self.db._lock:
+            row = self.db._conn.execute("SELECT * FROM ledger_meta WHERE id=1").fetchone()
+            assert row is not None
+            equity = float(row["equity"]) + float(amount)
+            available = float(row["available"]) + float(amount)
+            if available < -1e-9:
+                raise RuntimeError("可用资金不足")
+            self.db._conn.execute(
+                "UPDATE ledger_meta SET equity=?, available=?, updated_at_ms=? WHERE id=1",
+                (equity, available, now),
+            )
+            self.db._conn.execute(
+                "INSERT INTO ledger_entries(group_id, kind, amount, balance_after, note, ts_ms) VALUES (?,?,?,?,?,?)",
+                (group_id, kind, float(amount), equity, note, now),
+            )
+            self.db._conn.commit()
+            return equity
+
+    def get_setting_float(self, key: str, default: float) -> float:
+        v = self.db.get_setting(key)
+        if v is None or v == "":
+            return default
+        try:
+            return float(v)
+        except ValueError:
+            return default
+
+    def get_setting_int(self, key: str, default: int) -> int:
+        return int(self.get_setting_float(key, float(default)))