Add configurable SIM equity (default 10k) and strategy docs.

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

backend/app/sim/ledger.py

@@ -48,6 +48,24 @@ class Ledger:
             self.db._conn.commit()
             return equity
 
+    def reset_equity(self, amount: float, *, note: str = "重置模拟资金") -> float:
+        """将权益与可用资金重置为 amount（reserved 清零）。须在无持仓时调用。"""
+        now = int(time.time() * 1000)
+        amt = float(amount)
+        if amt < 0:
+            raise ValueError("模拟资金不能为负")
+        with self.db._lock:
+            self.db._conn.execute(
+                "UPDATE ledger_meta SET equity=?, available=?, reserved=0, updated_at_ms=? WHERE id=1",
+                (amt, amt, now),
+            )
+            self.db._conn.execute(
+                "INSERT INTO ledger_entries(group_id, kind, amount, balance_after, note, ts_ms) VALUES (?,?,?,?,?,?)",
+                (None, "reset", amt, amt, note, now),
+            )
+            self.db._conn.commit()
+            return amt
+
     def get_setting_float(self, key: str, default: float) -> float:
         v = self.db.get_setting(key)
         if v is None or v == "":