ci: install dev deps and generate requirements.txt for Snyk

[Pymetheus]

Description

Simplify the security workflow by removing the astral-sh/setup-uv steps and the uv sync/export flow. Instead of installing individual packages, the workflow now runs pip install -e . --group dev and pip freeze > requirements.txt to produce a requirements.txt file for Snyk scanning. This reduces duplication and uses the project's dev extras for dependency installation.
This change assures Snyk has all required dependencies.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Code refactoring
• Performance improvement
• Test addition or update

Related Issue

Snyk was silently failing with exit code 2, as dependency installation with uv was not sufficient

Changes Made

• updated security workflow with pip install -e . --group dev and pip freeze > requirements.txt for Snyk scanning

Testing

Describe how you tested your changes:

• Unit tests pass
• Integration tests pass
• Manual testing performed

Screenshots (if applicable)

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Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have updated the documentation accordingly
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Additional Context

Add any other context about the PR here.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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