chore: Migrate from Poetry to uv workspace

[jsonbailey]

Note

Medium Risk
Build/release tooling is refactored across CI and packaging; risk is mainly around dependency resolution and publishing artifacts changing with the new uv/hatchling pipeline.

Overview
Migrates the repo from Poetry to a uv workspace with a shared root .venv, updating root and package pyproject.toml files to PEP 621 [project] metadata, dependency-groups, and hatchling builds.

CI and release workflows now set up uv (via astral-sh/setup-uv) and install deps with uv sync instead of installing Python + Poetry; package Makefiles switch install/lint/test/build/docs to uv run and uv build.

Housekeeping: ignore uv.lock and .venv/, and update CONTRIBUTING.md/imports formatting to reflect the new tooling.

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