Add BlockReq Polygon public RPC after latest-block repair

[luanxu-dev]

If you are adding a new RPC, please answer the following questions.

Link the service provider's website (the company/protocol/individual providing the RPC):

https://blockreq.com/

Public endpoint documentation: https://blockreq.com/docs/build/public-endpoints/

This draft appends the BlockReq Polygon mainnet HTTPS public RPC to chain 137. The other 24 verified EVM RPCs are submitted separately in #3213.

Provide a link to your privacy policy:

No public RPC privacy-policy URL could be verified for this submission. This entry uses tracking: "unspecified"; no privacy or retention claim is made.

If the RPC has none of the above and you still think it should be added, please explain why:

The service provider website and public endpoint documentation are available. Missing privacy information is explicitly disclosed above.

Draft: please do not merge until the latest-block probe succeeds.

Point-in-time checks on 2026-10-01 at approximately 17:51 UTC, followed by a repeat check:

• eth_chainId returns 0x89 (137).
• eth_blockNumber succeeds.
• POST supports Origin https://chainlist.org; OPTIONS preflight returns HTTP 204.
• Chainlist's actual query, eth_getBlockByNumber(["latest", false]), currently returns JSON-RPC error -32601: method ignored by upstream: method ignored by upstream configuration.
• The documented legacy Polygon gateway has the same latest-block failure and is not a working substitute.
• The entry is appended to the array and npm test passes syntax and duplicate-key checks. The repository does not define a preflight script.

The public Polygon route needs to be repaired and this exact query rechecked before marking this PR ready for review. Keeping it separate allows the other 24 verified endpoints to be reviewed independently.

Your RPC should always be added at the end of the array.