Integrate Open CryptoPay payment standard

[reubenyap]

Summary

Adds Open CryptoPay QR support with method/network validation, quote expiry checks, fee-floor enforcement, and raw signed transaction submission where required by the OCP flow.

This also adds minimal Ethereum mainnet ERC-20 support for tokens already enabled in the wallet. ERC-20 matching uses the token contract address from the EIP-681 transaction URI as the authority; symbols are only used for display and initial asset filtering.

Supported OCP Flows

• Detects Open CryptoPay URLs embedded in QR LNURL payloads.
• Fetches payment details and quotes over HTTPS.
• Filters available payment methods by wallet coin, OCP method, network, and enabled token contract.
• Supports native ETH through the existing send flow.
• Supports enabled Ethereum mainnet ERC-20 tokens through TokenSendView.
• Submits raw signed hex to the OCP provider for EVM/ERC-20, BTC, and Firo instead of broadcasting locally first.
• Keeps non-OCP send and token-send behavior unchanged.

Safety Checks

• Rejects unsupported methods such as Lightning/BinancePay/unknown chains.
• Rejects ERC-20 URIs unless they are Ethereum mainnet transfer calls with recipient, raw amount, and an enabled matching contract.
• Enforces quote expiration before opening send and again immediately before OCP submission.
• Enforces OCP minFee for supported fee models.
• Verifies recipient, amount, method, asset, and token contract before provider submission.
• Uses HTTPS-only OCP calls, callback host validation, and request timeouts.

Limitations

• ERC-20 support is limited to Ethereum mainnet tokens already enabled in the wallet.
• No token auto-import, custom-token lookup, token chooser UI, Polygon/Base/Arbitrum/BSC support, Lightning support, BinancePay support, or Monero OCP support is added.
• OCP callback host validation assumes the callback host matches the LNURL host.

Test Plan

• Added parser coverage for native ETH and ERC-20 EIP-681 URIs.
• Covered invalid chain id, wrong function, missing recipient, missing amount, and malformed token contract cases.
• Manually reviewed native ETH and ERC-20 routing paths.
• Verified OCP-only raw signing paths are gated behind OpenCryptoPayCommit.
• Ran formatting and diff whitespace checks.