More v2 frame related infra

1. All cast objects now natively include v2 frame metadata as part of embed information

2. New API that returns a list of v2 frames: https://docs.neynar.com/reference/fetch-frame-catalog

3. Metadata crawl API where you can put in any URL and get embed information, allows showing v2 frame previews in cast composers: https://docs.neynar.com/reference/fetch-embedded-url-metadata

s/o @rafi for the work, reach out with questions and feedback 🪐

Engineering @neynar. Amusement, wonder, and uncertainty ✴︎ libred.org

building farcaster infra @ /neynar 🪐 casting @ /rish