Encode beasts into token IDs

[loothero]

Summary

• encode Beast ERC721 token IDs directly from PackableBeast attributes
• remove stored token_id -> PackableBeast data and decode owned token IDs instead
• update minting, ranking, metadata, tests, and docs for packed token IDs and supply-count semantics

Notes

• Fresh deployments only; this intentionally does not support legacy sequential token IDs.
• Genesis and non-genesis Beasts use the same packed token ID format.
• total_supply() remains a count of minted NFTs, not the largest token ID.

Tests

• scarb fmt --check --workspace
• scarb build
• snforge test --max-n-steps 4294967295

[gemini-code-assist]

Code Review

This pull request transitions the Beasts NFT collection to a deterministic token ID system, where the ERC721 token_id is a 53-bit packed representation of a beast's attributes. This architectural shift removes the need for the beasts storage map, as attributes are now decoded directly from the ID. The update includes refactoring the beasts_nft contract, ranking logic, and metadata generation, alongside comprehensive updates to the test suite to accommodate packed IDs. I have no feedback to provide as no review comments were submitted.