feat: 消除同访草案机制，改为查询时通过 companions 数组覆盖

- 删除 POST /visits 中的草案创建逻辑（不再创建空拜访记录）
- 周报查询：manager 角色也显示同访的拜访记录
- 亮灯表覆盖：同访人也算客户拜访覆盖（UNION companions）
- 填报进度：同访人也算今日已填报
- 清理已有 2 条空草案记录

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

backend/app/api/visits.py

@@ -194,22 +194,6 @@ async def create_visit(
         )
         db.add(log)
 
-    # Create draft copies for companions
-    for companion_id in data.companions:
-        if companion_id != uuid.UUID(current_user["user_id"]):
-            draft = Visit(
-                customer_id=data.customer_id,
-                visit_date=parse_date(data.visit_date),
-                visit_method=data.visit_method,
-                time_range=data.time_range,
-                communication_content="",  # Leave blank for companion to fill
-                customer_demand="",
-                companions=[],
-                photos=[],
-                manager_id=companion_id,
-            )
-            db.add(draft)
-
     await db.commit()
     await db.refresh(visit)
     return await _enrich_visit(visit, db)