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

completions/genpass.zsh

@@ -1,10 +1,21 @@
 #compdef genpass
 _arguments \
-  '--length[-l]:password length:' \
-  '--count[-n]:number of passwords:' \
-  '--lower[use lowercase letters]' \
-  '--upper[use uppercase letters]' \
-  '--digits[use digits]' \
-  '--symbols[use symbols]' \
-  '--symbol-set[custom symbol set]' \
-  '--no-ensure[do not enforce each type]'
+  '-h[show help]' \
+  '--help[show help]' \
+  '-l[password length]:length:' \
+  '--length[password length]:length:' \
+  '-n[number of passwords]:count:' \
+  '--count[number of passwords]:count:' \
+  '--lower[include lowercase letters]' \
+  '--upper[include uppercase letters]' \
+  '--digits[include digits]' \
+  '--symbols[include symbols]' \
+  '--symbol-set[custom symbol set]:symbols:' \
+  '--no-ensure[disable ensure-each-type rule]' \
+  '--no-ambiguous[exclude ambiguous characters (l, 1, I, O, 0)]' \
+  '--entropy[show password entropy]' \
+  '-c[copy to clipboard]' \
+  '--clipboard[copy to clipboard]' \
+  '--format[output format]:format:(plain json delimited)' \
+  '--config[show current configuration]' \
+  '--save-config[save options as defaults]'