* fix: update build system and Python version support for 3.10+ compatibility

* chore: fix pre-commit version + regenerate poetry.lock for Python 3.10+ compatibility

* fix: bump py to 1.11.0 to fix pytest startup on Python 3.11

* fix: revert build backend to poetry.core.masonry.api for pip compatibility

* add get_rate_estimate method

* fix get_rate_estimate return type

* chore: bump pre-commit hook versions for Python 3.12 / click 8.1

black 20.8b1 was broken against click>=8.1 (ImportError: _unicodefun),
and flake8 3.9.2 was broken on Python 3.12 (EntryPoints.get removed).
Bumps black, flake8, their transitive plugins, and blacken-docs to
currently-maintained versions.

* chore: remove invalid 'safe = true' from [tool.black] in pyproject.toml

Modern black does not recognize 'safe' as a pyproject config key and
emits "Invalid config keys detected: 'safe'" on every run. --safe is
still the default CLI behavior, so removing the key is a no-op for
actual formatting.

* chore: apply black 24 reformat and fix flake8 lint errors

Applies black 24.10.0 formatting to the repo (mostly trailing-comma
and blank-line-after-module-docstring changes from 4 years of black
style evolution) and fixes the 29 E501 line-length errors plus 1 D419
empty-docstring that the upgraded flake8 surfaced. Bundled together
because the formatting hook and the lint hook block each other in
intermediate states — keeping them in one commit avoids a red
midpoint in the series.

* chore: bump black and flake8 dev-deps to align with pre-commit

black ^22.0.0 -> ^24.0.0 and flake8 ^6.0.0 -> ^7.0.0 so that
'poetry run black' / 'poetry run flake8' (and editor integrations
using the poetry venv) produce the same output as the pre-commit
hooks. Regenerates poetry.lock; transitive bumps are scoped to
black/flake8 deps only (packaging, pycodestyle, pyflakes,
typing-extensions).

* chore: pin pre-commit flake8 to 7.3.0 to match poetry-resolved version

Keeps the pre-commit hook and the poetry dev-dep on the exact same
flake8 version so local and CI runs can't diverge.

Co-authored-by: Joshua Semar <joshua.semar@shipstation.com>

python-dotenv was declared as a runtime dependency but is never imported
or used anywhere in the package. Removing it reduces unnecessary overhead
for downstream consumers.

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Explains how commit message format drives release-please automation
and ultimately PyPI publishing.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Release-As: 2.1.1

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>