branch_scanner: 修price_lower遗漏+只输最优分支

1. check_condition 新增 price_lower 检查（买入区下界）
   之前 buy_dip 分支的 price_lower: >=entry_low 从未被验证
   导致跌出买入区的股票也错误触发买入信号

2. 输出改为每只股票只列最优优先级的适用分支
   之前列出所有适用分支（多分支冲突：同一只股同时止损+买入）
   优先级：止损(P0) > 回调买入(P1) > 追涨(P2) > 减仓(P3) > 止盈(P4) > 持有(P99)
   每只股票只列一项，无矛盾

data/price_history.json

@@ -107,8 +107,8 @@
     {
       "date": "2026-06-24",
       "high": 88.32,
-      "low": 83.23,
-      "close": 83.23
+      "low": 83.0,
+      "close": 83.02
     }
   ],
   "00700": [
@@ -1284,7 +1284,7 @@
       "date": "2026-06-24",
       "high": 68.8,
       "low": 65.92,
-      "close": 66.98
+      "close": 67.09
     }
   ],
   "300548": [
@@ -2316,7 +2316,7 @@
       "date": "2026-06-24",
       "high": 745.2,
       "low": 660.01,
-      "close": 685.03
+      "close": 684.0
     }
   ],
   "688802": [
@@ -2609,8 +2609,8 @@
     {
       "date": "2026-06-24",
       "high": 52.43,
-      "low": 49.71,
-      "close": 49.73
+      "low": 49.05,
+      "close": 49.07
     }
   ],
   "002171": [