Add Oxin Chain (4457) with official icon

[oxinchain]

Adding Oxin Chain to the ethereum-lists/chains registry. Oxin Chain is a Proof-of-Authority (PoA) based EVM-compatible blockchain designed for high performance and low-cost transactions.

Chain Details
Name: Oxin Chain

Chain ID: 4457

Currency Symbol: OXIN

Network Type: Mainnet (PoA)

Official Links
Website: https://oxinchain.io/

Block Explorer: https://scan.oxinchain.io/

RPC Endpoints
These are the official public nodes maintained by the Oxin Foundation:

https://rpc.oxinchain.io/

https://rpc1.oxinchain.io/

https://rpc2.oxinchain.io/

Icon Information
The official logo has been uploaded to IPFS and the metadata is provided in the _data/icons folder.

IPFS CID: bafkreibppuijktkbw75jrng6w5xbrvvh6w5ppd4msriiruibmpk25pndmi

Compliance
[x] JSON files formatted via Prettier.

[x] Filename follows CAIP-2 standard (eip155-4457.json).

[x] Icon size is under 250KB and follows specified constraints.

[github-actions]

You successfully submitted a PR! Due to the amount of PRs coming in: we will only look at PRs that the CI is happy with. We can also not hold your hand getting the CI green - just look how others that where merged did it and RTFM. So as long as there is any CI check that reports an error - no human will look at this. You might be able to ask for some support after supporting the project - e.g. by sending funds to lists.eth. When you fixed things after a requested change - then you also need to (re-)request a review.