No-packing fine-tuning jobs now priced on len(dataset) max_seq_length tokens

Rolled out a pricing update for no-packing fine-tuning jobs. When the no-packing option is chosen, the number of training dataset tokens is now calculated as len(dataset) * max_seq_length to account for the compute used by packing-free jobs.

• max_seq_length is configurable in both the SDK and UI.
• Price prediction reflects these changes, so if no-packing is chosen you can control the cost of the job by adjusting the sequence length.