Feat/test suite infrastructure

[TrezorHannes]

PR: Add Testing Suite Infrastructure

Summary of Changes

• Introduced a comprehensive testing infrastructure using pytest and pytest-mock.
• Added unit tests for fee_adjuster.py (focusing on the recent "stuck channel" fix).
• Added unit tests for Magma/magma_sale_process.py (focusing on order handling and LND integration).
• Configured GitHub Actions to automatically run tests on every Pull Request.
• Updated documentation (fee_adjuster.md) with testing instructions.

Detailed Changes

• Infrastructure:
  • requirements-dev.txt: Added pytest, pytest-mock, requests-mock.
  • tests/conftest.py: Added shared fixtures for fee configuration.
  • .github/workflows/tests.yml: New CI workflow.
• Other/fee_adjuster.py:
  • Validated logic for stuck channel discounts and premium application via tests/test_fee_adjuster.py.
• Magma/magma_sale_process.py:
  • Validated accept_order, reject_order, execute_lnd_command, and execute_lncli_addinvoice via tests/Magma/test_magma_sale_process.py.
  • Utilized sys.modules patching to mock global side-effects (telebot, configparser).

Testing Strategy

• Unit Tests:
  • Fee Adjuster: Verified the core mathematical logic for fee bands, ensuring discounts are gated correctly by stuck status.
  • Magma: Verified API interactions and shell command parsing. Mocked all external dependencies (Amboss API, LND CLI, Telegram, Config) to ensure tests are fast, reliable, and run in isolation.
• Verification Result: 12/12 tests passing locally ✅.

What's Left for Later

• Expand test coverage to LNDg/ scripts (e.g., amboss_pull.py, channel_base-fee.py).
• Add integration tests if a mock LND node environment becomes available.

Checklist

• Code follows project conventions
• All tests passing locally
• Documentation updated (fee_adjuster.md)