Improve wandb logging

[purzelrakete]

What

Update wandb logging.

Why

Have a look at the wandb logging guidelines. I did not know about summaries, or the fact that each call to wandb.log increments the step.

Acceptance Criteria

• [x] Collapse wandb.log calls so that step does not get unnecessarily incremented.
• [x] Introduce the epoch and track the actual step, maybe by setting step=actual_step.
• [x] Upload the generated audio at the end.
• [x] Use a summary instead of a logging call where appropriate.
• [x] Introduce panel sections with / as appropriate.