feat: update deps to bsv-rs 0.3.1 + bsv-wallet-toolbox-rs 0.3.1, fix e2e tests

- Update bsv-wallet-toolbox-rs dependency from 0.1 to 0.3
- Add abort cleanup in e2e_nosend_flow test to prevent UTXO pollution
- All 53 tests pass (45 synthetic + 8 E2E)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Calgooon