Lynn Gordon built French Meadow into a go-to Twin Cities café, and now she is asking a judge to help her take it back. In a new lawsuit, the founder wants last year's sale of the Minneapolis flagship on Lyndale Avenue undone, calling the deal "a horrible mistake." Her court filing says the buyer behind the location defaulted on most of the purchase financing and let the standards that made the café a local staple slip, with potential fallout for…