feat: 拜访记录创建时自动联动商机跟进

- POST /visits 创建拜访后，自动查询同客户下「跟进中」的商机
- 为每个匹配商机追加一条跟进记录（mini_business_log）
- 内容: 沟通内容 + 客户需求拼接
- 方式: 拜访方式自动映射（上门→上门/电话→电话/微信→微信/出差→其他）
- 仅创建时触发，更新/导入不联动

Co-Authored-By: Claude <noreply@anthropic.com>

backend/app/api/visits.py

@@ -167,6 +167,33 @@ async def create_visit(
         current_user["name"], "拜访自动完成",
     )
 
+    # Auto-create follow-up logs for active mini business opportunities
+    from app.models.mini_business import MiniBusiness
+    from app.models.mini_business_log import MiniBusinessLog
+    method_map = {"上门": "上门", "电话": "电话", "微信": "微信", "出差": "其他"}
+    active_biz = await db.execute(
+        select(MiniBusiness).where(
+            MiniBusiness.customer_id == data.customer_id,
+            MiniBusiness.status == "跟进中",
+        )
+    )
+    for biz in active_biz.scalars().all():
+        parts = []
+        if data.communication_content and data.communication_content.strip():
+            parts.append(f"沟通内容：{data.communication_content.strip()}")
+        if data.customer_demand and data.customer_demand.strip():
+            parts.append(f"客户需求：{data.customer_demand.strip()}")
+        log_content = "\n".join(parts) if parts else "拜访跟进"
+        follow_method = method_map.get(data.visit_method, "其他")
+        log = MiniBusinessLog(
+            business_id=biz.id,
+            log_date=parse_date(data.visit_date),
+            method=follow_method,
+            content=log_content,
+            created_by=uuid.UUID(current_user["user_id"]),
+        )
+        db.add(log)
+
     # Create draft copies for companions
     for companion_id in data.companions:
         if companion_id != uuid.UUID(current_user["user_id"]):