fix nano banana pro pricing and resolutions

[P3il4]

fixes two issues with current implementation of nano banana pro in togetherai:

1. not converting aspect ratio values into actual width and height parameters for togetherai, resulting in generation errors
2. incorrect pricing for 2K and 4K quality
   https://www.together.ai/models/nano-banana-pro
   1K and 2K cost 13.4, 4K costs 24. current implementation does 13.51 * quality value

testing:

puter.drivers.call("puter-image-generation", "together-image-generation", "generate", {
  "prompt": "generate an image of a cat",
  "ratio": {
    "w": 21,
    "h": 9
  },
  "quality": "2K",
  "model": "togetherai:google/gemini-3-pro-image"
})

should give correct width + height values and correct cost amount. other models should not be affected by this
wasn't able to test this with a real key as i don't have one but logging the request gave correct values.

[CLAassistant]

All committers have signed the CLA.

[ProgrammerIn-wonderland]

Aiming to merge this this week after testing to make sure there aren't billing bugs

[ProgrammerIn-wonderland]

LGTM