Tird

- Performed code refactoring.
- Added `log_d()`, `log_i()`, `log_w()`, `log_e()`; used them instead of raw `print()`.
- Improved log and prompt messages.
- Replaced `hashlib.blake2b` with `nacl.hashlib.blake2b`.
- Added docstrings and comments.
- Improved error handling; handled nonce counter overflow and `EOFError` for every `input()`.
- Changed the numbering of input options.
- Added limitations for input options set to: `1023` for passphrase size, `2^60` for output file size (in action 8), and `10^18` for maximum padding percentage.
- Applied `strip()` for integer and boolean input options.
- Improved type hinting using the features of Python 3.9; the minimum required version of Python has been updated to 3.9.
- Added `pyproject.toml`.
- Removed `setup.py`.

- Improve keyfile handling: all keyfiles from the specified directory are not accepted if there is no access to at least one subdirectory.
- Update UI.
- Update docs.
- Improve debug.

- Prevent an attempt to remove a non-existent output path.

- Add "offer to remove the output file path" feature.
- Update docs.

- Update UI.
- Update docs.
- Minor refactoring.

- Update docs.
- Update UI.
- Improve debug.
- Add deb/DEBIAN/control and update Makefile to build and install the package.