fix: restore custom_ route to _evaluate_v53 (was lost in scp overwrites)

backend/signal_engine.py

@@ -554,7 +554,7 @@ class SymbolState:
         # v53 → 统一评分（BTC/ETH/XRP/SOL）
         # v53_alt / v53_btc → 兼容旧策略名，转发到 _evaluate_v53()
         # v51/v52 → 原有代码路径（兼容，不修改）
-        if strategy_name.startswith("v53"):
+        if strategy_name.startswith("v53") or strategy_name.startswith("custom_"):
             allowed_symbols = strategy_cfg.get("symbols", [])
             if allowed_symbols and self.symbol not in allowed_symbols:
                 snap = snapshot or self.build_evaluation_snapshot(now_ms)