Feature Parity 20: Sign and Verify Message Flow

[johnny9]

Summary

Provide message signing and verification screens with parity behavior and warnings.

Complexity

• M

Dependencies

• 10
• 15
• 02

Global Constraints

• All implementation lives under gui-qml/.
• No GUI runtime dependency on bitcoin/src/qt components. Reused logic must be moved/ported into gui-qml/.
• Do not change interfaces::Wallet or interfaces::Node in this version.
• Issue completion must satisfy DefinitionOfDone.md.

Scope

• Add sign message flow using wallet sign API for eligible addresses.
• Add verify message flow using local verification utilities.
• Include phishing/safety warning copy and reset/copy helpers.
• Integrate address selection from contacts/address book when available.

Acceptance Criteria (DoD-Aligned)

1. User can sign message for valid wallet-owned signing address and copy signature.
2. User can verify signature/address/message combinations with correct success/failure states.
3. Unsupported address types are clearly explained.

Required Tests

• C++ unit tests: Unit tests for sign/verify adapter and validation logic.
• QML QTest: QTests for input validation, success/error states, and reset actions.
• Python E2E (qml/test/testbridge.h): E2E flow for valid sign/verify and invalid signature failure case.

Implementation Notes

• No reliance on qt/signverifymessagedialog.*.