Restore Python support without mach-nix

[sylvesterkaczmarek]

Fixes #6.

Restore Python project support without mach-nix. Python environments now use the Python interpreter from the pinned nixpkgs and a generated nix/python-packages.nix dependency list, while existing Python project configuration remains compatible.

This also restores Python in the support matrix, updates generated project guidance, adds focused rendering coverage, and bumps the version as required by the contribution guidelines.

Validation:

• nix flake check
• nix build
• evaluated a generated Python development-shell fixture against the pinned nixpkgs

[sylvesterkaczmarek]

@sd234678 Refreshed the commit metadata as SSH-verified 0fc1609; the branch is 0 behind and mergeable. I ran the repository CI path in a clean Nix container: nix flake check passed on aarch64-linux, the full Haskell test suite compiled and passed (1/1 suite), and nix build produced the 2.7.0.0 package/binary including the new Python package generation coverage. I also attempted the same check under Docker x86_64 emulation to mirror GitHub Actions, but that container failed before project evaluation/build because the emulated Nix runtime could not load its seccomp BPF program (Invalid argument); no project test failed. The actual GitHub x86_64 Build workflow is currently waiting at action_required for maintainer approval. Ready for review once that workflow is allowed to run.