Consolidate dependencies and fix critical issues

Consolidate dependencies and fix critical issues

- Add missing requests-cache==1.2.1 dependency
- Update fake-useragent from 2.0.3 to 2.2.0
- Consolidate all dependencies into pyproject.toml
- Add [project.optional-dependencies] with dev group
- Remove redundant requirements.txt and .requirements-lint.txt
- Update CI/CD workflow to use pip install .[dev]
- Update README with minimal changes
- Fix script entry points in pyproject.toml

Improve GUI error handling and documentation

- Add helpful error message when Tkinter is missing
- Update README with GUI installation instructions
- Fix installation test to handle missing Tkinter gracefully
- Users now get clear instructions if GUI dependencies are missing

updates

update configs

update configs; get tests passing