Part of Epic: #75 - RC2: Wallet & Security Infrastructure

Testing and QA, starting from the Blockchain-p2p-networking branch:

• Unit and integration tests for core modules (wallet creation, seed phrase, address, transaction logic)
• Validate memory usage/performance against benchmarks
• Test cross-platform compatibility (desktop/mobile)
• Usability and UI responsiveness QA on Slint UI
• Security tests for key storage & transaction signing
  Assignee: app/copilot-swe-agent
  Label: enhancement