Add dual exit modes: fixed USDT or premium multiple.

Net PnL (after estimated close fees) drives auto close; Plan/Settings expose the choice.

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

backend/app/strategy/exits.py

@@ -2,22 +2,48 @@ from __future__ import annotations
 
 from dataclasses import dataclass
 
+EXIT_MODE_FIXED = "fixed_usdt"
+EXIT_MODE_PREMIUM = "premium_multiple"
+
 
 @dataclass(slots=True)
 class ExitDecision:
     should_close: bool
     reason: str = ""
+    target: float = 0.0
+
+
+def resolve_exit_target(
+    *,
+    exit_mode: str,
+    net_profit_target: float,
+    premium_exit_multiple: float,
+    initial_premium: float,
+) -> tuple[float, str]:
+    """返回 (出场目标金额 USDT, 模式标记)。"""
+    mode = (exit_mode or EXIT_MODE_FIXED).strip().lower()
+    if mode == EXIT_MODE_PREMIUM:
+        mult = max(0.0, float(premium_exit_multiple))
+        return float(initial_premium) * mult, EXIT_MODE_PREMIUM
+    return float(net_profit_target), EXIT_MODE_FIXED
 
 
 def check_exits(
     *,
-    perp_upl: float,
+    net_pnl: float,
+    exit_mode: str,
+    net_profit_target: float,
+    premium_exit_multiple: float,
     initial_premium: float,
-    move_pct: float,
-    exit_move_pct: float,
 ) -> ExitDecision:
-    if initial_premium > 0 and perp_upl + 1e-9 >= initial_premium:
-        return ExitDecision(True, "premium_cover")
-    if exit_move_pct > 0 and move_pct + 1e-9 >= exit_move_pct:
-        return ExitDecision(True, "move_pct")
-    return ExitDecision(False, "")
+    """净盈利（预估全平后）≥ 所选模式目标则全平。"""
+    target, mode = resolve_exit_target(
+        exit_mode=exit_mode,
+        net_profit_target=net_profit_target,
+        premium_exit_multiple=premium_exit_multiple,
+        initial_premium=initial_premium,
+    )
+    if target > 0 and net_pnl + 1e-9 >= target:
+        reason = "premium_multiple" if mode == EXIT_MODE_PREMIUM else "fixed_usdt"
+        return ExitDecision(True, reason, target)
+    return ExitDecision(False, "", target)