feat: 成交指标新表+可控自动结算（默认关，仅新进结算中eligible）

按设计文档：SettlementTime起表；关开关清eligible；定时任务只结到期eligible单；打款走统一结单；指标从stats_since起幂等记账。不打开旧全局ORDER_AUTO_SETTLEMENT。

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

orders/migrations/0016_order_auto_settle_eligible.py

@@ -0,0 +1,22 @@
+# 订单 AutoSettleEligible + jituan 成交/自动结算配置与指标表
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('orders', '0015_merchantorderext_bossphone'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='order',
+            name='AutoSettleEligible',
+            field=models.BooleanField(
+                db_column='auto_settle_eligible',
+                db_index=True,
+                default=False,
+                verbose_name='允许自动结算',
+            ),
+        ),
+    ]