Maint/deprecate requirements txt

[rugeli]

Problem

closes #459

Solution

• removed the per-platform requirements.txt files and the workflow that generates them
• updated Dockerfile.ecs to use uv sync against uv.lock, so dependency versions stay pinned
• added a new [dependency-groups].server = ["aiohttp"] group to declare the web-server dependency
• updated documentation

Type of change

• Maintenance (non-breaking change which preserves existing functionality)

Steps to Verify:

1. pull the branch and run uv sync --group server, it should resolve and install aiohttp along with the rest of the deps from uv.lock
2. (optional) rundocker build -f docker/Dockerfile.ecs -t cellpack-ecs, the image should build
3. (optional) rundocker run -p 80:80 cellpack-ecs then go to http://0.0.0.0:80/hello, should return Hello from the cellPACK server

[github-actions]

Packing analysis report

Analysis for packing results located at cellpack/tests/outputs/test_spheres/spheresSST

Ingredient name	Encapsulating radius	Average number packed
ext_A	25	236.0

Packing image

Distance analysis

Expected minimum distance: 50.00
Actual minimum distance: 50.01

Ingredient key	Pairwise distance distribution
ext_A

[rugeli]

initially I used pip install ".[server]", but that resolves fresh from PyPI on each build which means rebuilds could pick up different versions. Switching to uv sync keeps the install pinned to uv.lock, giving us more consistent builds.

[ascibisz]

just tried running this locally and it worked perfectly!

[Copilot]

Pull request overview

This PR removes legacy, autogenerated per-platform requirements.txt artifacts in favor of using uv.lock/uv sync for pinned dependency installation (notably for the ECS Docker image), and formalizes the web server dependency as an optional extra.

Changes:

• Deleted per-platform requirements.txt files and removed the GitHub workflow that generated them.
• Added a server optional dependency (aiohttp) and updated uv.lock accordingly.
• Updated docker/Dockerfile.ecs to install dependencies via uv sync (frozen + pinned) and adjusted docs to no longer reference the removed requirements files.

Reviewed changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
uv.lock	Adds aiohttp (and transitive deps) plus server extra metadata to keep installs pinned via uv sync.
pyproject.toml	Introduces [project.optional-dependencies].server and removes requirements from build source include.
docker/Dockerfile.ecs	Switches ECS image dependency installation from requirements+pip to uv sync --frozen --extra server.
docs/CONTRIBUTING.md	Removes the requirements install step from contributor setup instructions.
README.md	Updates install steps to rely on pyproject.toml/pip install -e . rather than per-OS requirements files.
.github/workflows/make-requirements.yml	Removes the workflow that exported and opened PRs for requirements files.
requirements/linux/requirements.txt	Deleted (previously autogenerated export).
requirements/macos/requirements.txt	Deleted (previously autogenerated export).
requirements/windows/requirements.txt	Deleted (previously autogenerated export).

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[rugeli]

to address copilot's review comment(slightly out of scope): pip install -e .[dev] has been silently failing on main since the dev lives in [dependency-groups] and pip's [extra] syntax can't read. Switched the contributor setup to use uv sync instead.

[mogres]

Looks great -- thanks!!