Release-readiness polish for v0.1.0 and Zenodo prep

[Copilot]

This PR makes a focused release-readiness pass for the first public release by tightening README release signals, adding an initial changelog, and polishing citation/package metadata for Zenodo onboarding without inventing a DOI.

• README release visibility

  • Added top-level badges for CI, Apache 2.0 license, and latest GitHub release.
  • Removed the fake DOI placeholder from the BibTeX block and replaced it with explicit post-Zenodo wording.

• Changelog for first public release

  • Added root CHANGELOG.md.
  • Created concise initial entry for v0.1.0 (2026-06-17) covering public release scope.

• Citation metadata polish

  • Updated CITATION.cff message to clarify DOI will be added after the first Zenodo-backed release.
  • Added date-released for 0.1.0.
  • Intentionally did not add a DOI field yet.

• Python project metadata polish

  • Added conservative project.classifiers in pyproject.toml (status, audience, Python versions, topic).
  • Added standard project.urls (Homepage, Repository, Issues, Changelog).

[![CI](https://github.com/beanapologist/Jump-Diffusion-Engine/actions/workflows/ci.yml/badge.svg)](...)
[![License: Apache-2.0](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](...)
[![GitHub release](https://img.shields.io/github/v/release/beanapologist/Jump-Diffusion-Engine)](...)

Post-merge follow-up after Zenodo is enabled: update README.md and CITATION.cff with the minted DOI and add a DOI badge.