Expands the confirm-tx warning system with three new warning types, all using the existing `visibility:hidden/visible` pattern from PR #98 (no animations, no layout shift).
## Changes
1. **Scam address list expanded** (7 → 652 addresses): Sourced from [MyEtherWallet/ethereum-lists](https://github.com/MyEtherWallet/ethereum-lists) darklist (MIT license). Checked synchronously before sending.
2. **Contract address warning**: When the recipient is a smart contract (detected via `getCode`), shows a warning that sending directly to a contract may result in permanent loss of funds.
3. **Null/burn address warning**: Detects known burn addresses (`0x0000...0000`, `0x...dead`, `0x...deadbeef`) and warns that funds are permanently destroyed.
4. **No-history warning** (existing from #98): Unchanged, still shows for EOAs with zero transaction history.
All warnings use reserved-space `visibility:hidden/visible` elements — no layout shift, no animations.
closes#114
Co-authored-by: clawbot <clawbot@noreply.git.eeqj.de>
Co-authored-by: user <user@Mac.lan guest wan>
Co-authored-by: clawbot <clawbot@eeqj.de>
Reviewed-on: #118
Co-authored-by: clawbot <sneak+clawbot@sneak.cloud>
Co-committed-by: clawbot <sneak+clawbot@sneak.cloud>
