Use BAF logo as default NFT image

[Sladuca]

Currently the default image for an NFT minted to the contract is the NEAR logo. This should be an SVG BAF logo

Tasks

• Get/create an SVG version of the BAF logo and use a tool to optimize it (make it small)
• Set DATA_IMAGE_NEAR_SVG_LOGO to the BAF logo's raw SVG text and rename the variable so it's clear that it's the BAF logo.