feat: recommend Python 3.12

[lsorber]

Changes:

• Recommend using Python 3.12 for packages and Python 3.13 for apps
• Fix Python version not being selected correctly in GitHub Actions
• Upgrade root Python to 3.13

[Copilot]

Pull request overview

This PR updates the recommended Python versions for the substrate project template, upgrading from Python 3.10/3.12 to Python 3.12/3.13. Apps are now recommended to use Python 3.13, while packages should use Python 3.12 as their minimum version. The PR also fixes a bug where GitHub Actions tests were using a hardcoded Python version instead of testing across the matrix of versions.

Key changes:

• Updated default Python version recommendations: 3.13 for apps, 3.12 for packages
• Fixed GitHub Actions to use matrix Python version instead of hardcoded value
• Upgraded project's own Python requirement to 3.13

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
uv.lock	Regenerated lockfile for Python 3.13, removing Python 3.10-3.12 specific wheels
test.sh	Updated hardcoded Python version from 3.10 to 3.12 for test scaffolding
pyproject.toml	Changed requires-python from ">=3.10" to ">=3.13,<3.14"
copier.yml	Updated template defaults: apps use 3.13, packages use 3.12 (previously 3.12 and 3.10)
.github/workflows/test.yml	Fixed to use matrix.python-version instead of hardcoded "3.10" for proper multi-version testing
.devcontainer/devcontainer.json	Updated base image from python3.10-trixie to python3.13-trixie

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