Move from circleci to GitHub completely

[michal-granec]

For: https://github.com/fetlife/fetlife-web/issues/35323

This PR finalizes our complete move away from CircleCI.

Changes:

• Add Ruby version matrix
• store test results
• Fix test not running on PR
• Remove CircleCI configuration

[Copilot]

Pull Request Overview

This PR completes the migration from CircleCI to GitHub Actions for CI/CD. It removes the CircleCI configuration entirely and enhances the GitHub Actions workflow with a Ruby version matrix, test result artifacts, and proper PR trigger configuration.

Key Changes:

• Implements a Ruby version matrix (2.4 through 3.3) for comprehensive testing across multiple Ruby versions
• Adds test result artifact upload with JUnit XML format for better test reporting
• Fixes the pull_request trigger to run on all PRs regardless of target branch
• Removes the CircleCI configuration file completely

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
.github/workflows/test.yml	Enhanced with Ruby version matrix (2.4-3.3), test result artifacts, and corrected PR trigger configuration
README.md	Updated CI badge from CircleCI to GitHub Actions
.circleci/config.yml	Removed as part of complete migration to GitHub Actions

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