feat(market_scanner): 增加4H趋势中性允许选项以优化信号处理逻辑

在市场扫描逻辑中引入了配置选项 `AUTO_TRADE_ALLOW_4H_NEUTRAL`，允许在逆势情况下不清零信号强度，便于推荐与列表展示。此改动旨在提升策略灵活性，同时确保策略层仍然禁止逆势自动下单，增强了系统的可用性与用户友好性。

trading_system/market_scanner.py

@@ -840,14 +840,16 @@ class MarketScanner:
                     if trend_4h in ('down', 'neutral', None) and direction == 'SELL':
                         signal_strength += TREND_SIGNAL_WEIGHTS['price_above_ema20']
             
-            # 4H趋势确认加分
+            # 4H趋势确认加分 / 逆势是否清零
+            allow_4h_neutral = bool(config.TRADING_CONFIG.get("AUTO_TRADE_ALLOW_4H_NEUTRAL", False))
             if direction and trend_4h:
                 if (direction == 'BUY' and trend_4h == 'up') or (direction == 'SELL' and trend_4h == 'down'):
                     signal_strength += TREND_SIGNAL_WEIGHTS['4h_trend_confirmation']
                 elif (direction == 'BUY' and trend_4h == 'down') or (direction == 'SELL' and trend_4h == 'up'):
-                    # 逆势信号，直接拒绝
-                    signal_strength = 0
-                    direction = None
+                    # 逆势时：若开启「允许4H中性」，仅不加分、不清零，便于出推荐与列表展示；策略层仍会禁止逆势自动下单
+                    if not allow_4h_neutral:
+                        signal_strength = 0
+                        direction = None
             
             # 强度上限归一到 0-10
             signal_strength = max(0, min(int(signal_strength), 10))