feat: 收款与提现商户拆分，支持后台上传证书

收款仍用 mch_id/mch_key；提现优先 withdraw_mch_id（空则回落）；证书分 pay/withdraw 目录落盘。退款逻辑未改。

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

jituan/migrations/0013_club_pay_withdraw_split.py

@@ -0,0 +1,70 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('jituan', '0012_club_mch_key'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='club',
+            name='pay_cert_path',
+            field=models.CharField(
+                blank=True, default='', help_text='apiclient_cert.pem，退款/V2 证书用',
+                max_length=512, verbose_name='收款商户证书路径',
+            ),
+        ),
+        migrations.AddField(
+            model_name='club',
+            name='pay_key_path',
+            field=models.CharField(
+                blank=True, default='', help_text='apiclient_key.pem，退款/V2 证书用',
+                max_length=512, verbose_name='收款商户私钥路径',
+            ),
+        ),
+        migrations.AddField(
+            model_name='club',
+            name='withdraw_mch_id',
+            field=models.CharField(
+                blank=True, default='', help_text='空则回落收款商户号 mch_id',
+                max_length=32, verbose_name='提现商户号',
+            ),
+        ),
+        migrations.AlterField(
+            model_name='club',
+            name='mch_id',
+            field=models.CharField(blank=True, default='', max_length=32, verbose_name='收款商户号'),
+        ),
+        migrations.AlterField(
+            model_name='club',
+            name='pay_app_id',
+            field=models.CharField(blank=True, default='', max_length=32, verbose_name='收款AppID'),
+        ),
+        migrations.AlterField(
+            model_name='club',
+            name='mch_key',
+            field=models.CharField(blank=True, default='', max_length=128, verbose_name='收款APIv2密钥'),
+        ),
+        migrations.AlterField(
+            model_name='club',
+            name='api_v3_key',
+            field=models.CharField(blank=True, default='', max_length=128, verbose_name='提现APIv3密钥'),
+        ),
+        migrations.AlterField(
+            model_name='club',
+            name='cert_serial_no',
+            field=models.CharField(blank=True, default='', max_length=64, verbose_name='提现证书序列号'),
+        ),
+        migrations.AlterField(
+            model_name='club',
+            name='private_key_path',
+            field=models.CharField(blank=True, default='', max_length=512, verbose_name='提现商户私钥路径'),
+        ),
+        migrations.AlterField(
+            model_name='club',
+            name='platform_cert_dir',
+            field=models.CharField(blank=True, default='', max_length=512, verbose_name='提现平台证书目录'),
+        ),
+    ]