ci: add CI with lint, unit, E2E, and code quality checks

[pv-rahil]

his PR introduces a complete CI/CD pipeline and refactors the testing infrastructure to improve reliability, stability, and long-term maintainability. It also enforces strict linting standards across the entire codebase, highlighted by the integration of pylint into the validation process.

Key Changes

CI/CD Integration

Added .github/workflows/tests.yml to automate:

• Linting and static analysis via pre-commit
• Unit tests with enforced coverage thresholds
• E2E tests using Dogtail for UI validation
• Allure reports published to GitHub Pages

Test Infrastructure Improvements

• Mocked QThread and ToastManager globally in conftest.py to prevent threading issues and unintended UI instantiation during unit tests
• Improved E2E test stability through:
  • More reliable UI element detection
  • Better cleanup between test scenarios
  • Timing adjustments tailored for CI environments
• Introduced unit_tests/factories/ to centralize test data generation and reduce duplication
• Removed redundant mocks and improved overall test case clarity and maintainability
• In wallet_transfer_selection_view_model_test.py, mocked LnNodeServerManager to prevent Qt signal connections during unit tests.

UI / Logic Improvements

• Added disable-button logic in the Close Channel Detail dialog to prevent double-clicks during channel closure operations

Source Code Updates

• Enabled and enforced pylint across the entire project
• Updated multiple files (viewmodels, views, repositories, etc.) to:
  • Fix formatting and lint issues
  • Eliminate code duplication
  • Reduce method complexity
  • Improve overall readability and consistency

Build Script Enhancements

• Updated build_script.py and build_linux.sh with:
  • Improved error handling
  • Additional validation checks

Dependencies

• Updated pyproject.toml and poetry.lock to support:
  • Revised testing requirements
  • CI/CD and linting integrations