Dynamic pool page OG image

[garethfuller]

Use params to generated different pool page OG image for cow pools: https://nextjs.org/docs/app/api-reference/file-conventions/metadata/opengraph-image#props

• [ ] We first need the default pool page image to be a png instead of jpg as this seems to be the only way to dynamically load it on the Edge.

[garethfuller]