fix(chat): 分销付款改为进入账号群，不再另建订单群

主站、分站和分站之间都只用发布时的账号群，二维码仍跟这个群走。

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

backend/internal/modules/chat/participant.go

@@ -75,13 +75,12 @@ func (r *Repository) CountUnreadMessages(ctx context.Context, principal Principa
 		Where("(cp.last_read_at IS NULL OR cm.created_at > cp.last_read_at)")
 
 	if principal.Type == "user" {
+		siteID := uint64(0)
 		if site != nil {
-			siteFilter := "(c.distribution_site_id = ? OR (c.order_id IS NOT NULL AND c.order_id IN (SELECT ro.id FROM rental_orders ro WHERE ro.distribution_site_id = ? AND ro.distribution_mode != 'two_party_distributor_receive')))"
-			query = query.Where(siteFilter, site.ID, site.ID)
-		} else {
-			mainFilter := "(c.distribution_site_id IS NULL OR c.distribution_site_id = 0) AND (c.order_id IS NULL OR c.order_id NOT IN (SELECT ro.id FROM rental_orders ro WHERE ro.distribution_site_id IS NOT NULL AND ro.distribution_site_id > 0 AND ro.distribution_mode != 'two_party_distributor_receive'))"
-			query = query.Where(mainFilter)
+			siteID = site.ID
 		}
+		filter, args := userSiteConversationFilter(siteID, principal.ID)
+		query = query.Where(filter, args...)
 	}
 
 	var total int64