Bug 1: getFullWarnings returned early for contract addresses, skipping
checkEtherscanLabel. Restructured to use isContract flag so the Etherscan
check runs for all addresses (contracts are often the most dangerous).
Bug 2: confirmTx.js only handled 'contract' and 'new-address' warning types,
silently discarding 'etherscan-phishing'. Added confirm-etherscan-warning
HTML element and handler in the async warnings loop.
Style: converted inline style attributes on phishing warning banners
(approve-tx, approve-sign, approve-site) to Tailwind utility classes
(bg-red-100 text-red-800 border-2 border-red-600 rounded-md).
