Add Python package build infrastructure with pyproject.toml

[Copilot]

The CONTRIBUTING.md referenced python -m build but the required pyproject.toml was missing and excluded from git, preventing package builds.

Changes

• Created pyproject.toml: PEP 517/518 compliant build configuration with package metadata, dependencies, and setuptools backend
• Updated .gitignore: Removed pyproject.toml exclusion, added build/ directory
• Created BUILD_INSTRUCTIONS.md: Complete build workflow covering prerequisites, build steps, PyPI upload, version updates, and troubleshooting
• Created QUICKSTART_BUILD.md: TL;DR reference for common build tasks
• Updated CONTRIBUTING.md: Reference new docs, update version file path from setup.py to pyproject.toml

Building the package

pip install --upgrade pip build twine
python -m build

Produces dist/planetprofile-3.0.0-py3-none-any.whl and .tar.gz source distribution.

Version updates

Update version in both:

• pyproject.toml (line 6)
• PlanetProfile/Utilities/PPverNum.txt

Original prompt

I want to make this codebase into a python package. The Contributing.MD has a description but it says to run python -m build but this doesnt exist as a file. Read through the codebase and give me instructions on how to build a package

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