feat(market_scanner): 优化回退信号逻辑以提升信号处理能力

在市场扫描逻辑中调整了回退信号的计算方式，降低了信号强度为零时的触发条件，并引入24小时涨跌幅作为方向判断依据。这一改动旨在增强策略的灵活性，确保在市场波动时能够提供更有效的交易建议，同时提升用户体验。

trading_system/market_scanner.py

@@ -854,9 +854,10 @@ class MarketScanner:
             # 强度上限归一到 0-10
             signal_strength = max(0, min(int(signal_strength), 10))
 
-            # 回退：趋势逻辑过严时（MACD/EMA/4H 未同时满足），用 RSI/MACD/布林 综合得分给弱信号，避免长期全 0
-            if signal_strength == 0 and direction is None and signal_score >= 5:
-                fallback_strength = min(5, max(1, signal_score - 3))  # 5->2, 6->3, 7->4, 8+->5
+            # 回退：趋势逻辑过严时（MACD/EMA/4H 未同时满足），用 RSI/MACD/布林/涨跌 给弱信号，避免长期全 0
+            # 强度映射：signal_score 4->2, 5->3, 6->4, 7->5, 8->6, 9->7, 10->7（高得分可触达 MIN_SIGNAL_STRENGTH 7）
+            if signal_strength == 0 and direction is None and signal_score >= 4:
+                fallback_strength = min(7, max(2, signal_score - 2))
                 if rsi is not None:
                     if rsi < 35:
                         direction = 'BUY'
@@ -885,6 +886,17 @@ class MarketScanner:
                     elif current_price < ema20 < ema50:
                         direction = 'SELL'
                         signal_strength = fallback_strength
+                # 仍无方向时用 24h 涨跌给方向（便于出推荐/开单；强度用 fallback_strength，高得分可≥7）
+                if direction is None:
+                    change_pct = symbol_info.get('changePercent')
+                    try:
+                        ch = float(change_pct) if change_pct is not None else None
+                    except (TypeError, ValueError):
+                        ch = None
+                    if ch is not None:
+                        direction = 'BUY' if ch > 0.5 else ('SELL' if ch < -0.5 else None)
+                        if direction:
+                            signal_strength = fallback_strength
 
             # ===== 趋势状态缓存（用于后续“入场时机过滤”）=====
             try: