feat: add type hints, new CLI features, and improve project structure

chore: add uv.lock to gitignore

Major changes:
- Add type hints and docstrings to all functions (PEP 484)
- Add __main__.py for module execution (python -m genpass)
- Expose public API in __init__.py
- Add config file support (~/.genpass/config.json)
- Add entropy calculation (--entropy)
- Add clipboard support (--clipboard/-c)
- Add ambiguous characters exclusion (--no-ambiguous)
- Add output formats: plain, json, delimited (--format)
- Add sensible defaults (all character types enabled by default)
- Add input validation for length and count
- Update shell completions for all new options
- Add pre-commit config with ruff, mypy, black
- Update pyproject.toml with dev dependencies and tool configs
- Add requirements.txt and requirements-dev.txt
- Update README.md with comprehensive examples

BREAKING CHANGE: Default behavior now includes all character types

.gitignore

@@ -109,6 +109,9 @@ ipython_config.py
 #   https://pdm.fming.dev/#use-with-ide
 .pdm.toml
 
+# uv
+uv.lock
+
 # PEP 582; used by e.g. github.com/David-OConnor/pyflow and github.com/pdm-project/pdm
 __pypackages__/