Implement Acela NextGen tags

[Mr-Technician]

Amtrak highlights NextGen Acela trains with a "NextGen" tag:

The RailForLess API supports this, but is not implemented in the UI.

"travelLegs": [
            {
              "trainId": "2102",
              "route": "Acela",
              "origin": "WAS",
              "departureDateTime": "2026-05-01T05:55:00",
              "destination": "NYP",
              "arrivalDateTime": "2026-05-01T08:54:00",
              "elapsedSeconds": 10740,
              "type": "TRAIN",
              "isBorderCross": false,
              "isSelfTransfer": false,
              "amenities": [
                "Cafe",
                "Quiet Car",
                "Free WiFi",
                "Seat Selection",
                "Seat Display"
              ],
              "addItems": [
                {
                  "availableInventory": 8,
                  "fare": 49,
                  "type": "Pet"
                }
              ],
              "travelServiceTag": [
                "NextGen"
              ]
            }
          ]