fix: add bridged HRC721 mint and burn API

[blueforyou0202]

Summary

• add BridgedHRC721Token.mint(account, tokenId, txOptions) for the ABI's mint(address,uint256) function
• add burn(tokenId, txOptions) and burnFrom(owner, tokenId, txOptions) for the bridged HRC721 burn functions
• add focused unit coverage for the new SDK wrapper dispatches

Notes

This is a separate bridged HRC721 mint/burn API gap. It intentionally does not touch tokenURI, ownership/approval APIs, safe-transfer APIs, or overloaded safeMint handling.

Validation

• Docker node:16-bullseye with only this repo mounted
• npm ci --ignore-scripts --no-audit --fund=false
• ./node_modules/.bin/mocha -t 120000 --require ts-node/register src/tests/bridged-hrc721-token-mint-burn.spec.ts --exit with --network none
• ./node_modules/.bin/tsc --noEmit --pretty false -p tsconfig.json with --network none
• ./node_modules/.bin/eslint src/bridge/bridgedHrc721Token/index.ts src/tests/bridged-hrc721-token-mint-burn.spec.ts with --network none

Related: harmony-one/bounties#125