upgrade to specutils>2.0

[kelle]

This will make it possible to read more JWST spectra.

• raise minimum specutils to 2.0
• change class from Spectrum1D to Spectrum

[Copilot]

Pull Request Overview

This PR upgrades the specutils dependency from version 1.0+ to 2.0+ to enable reading more JWST spectra formats. The change involves updating the dependency constraint and replacing all references to the deprecated Spectrum1D class with the new Spectrum class from specutils 2.0.

• Update minimum specutils version requirement from 1.0 to 2.0
• Replace Spectrum1D class references with Spectrum throughout the codebase
• Update documentation and comments to reflect the class name change

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
pyproject.toml	Updates minimum specutils dependency from 1.0 to 2.0
docs/index.rst	Updates documentation references from Spectrum1D to Spectrum
astrodbkit/tests/test_spectra.py	Updates test mock to use Spectrum instead of Spectrum1D
astrodbkit/spectra.py	Updates all code references from Spectrum1D to Spectrum class

[dr-rodriguez]

Looks OK to me, and the tests are all passing.

[kelle]

Now we need a new release. :)