feat(KLEF): Add GitHub Actions workflows (CI, release, labeler)

[NathanRoos]

Pull Request

Summary

Adds GitHub Actions CI/CD workflows.

Related Issues

Closes #

---

Changes

What's Included

• ci.yml — runs a Docker image build on every push/PR to main
• release.yml — triggers on v* tags; builds and pushes the Docker image to ghcr.io/kleffio/alertmanager-alerting, creates a GitHub Release, and opens an auto-merged PR to plugin-registry bumping alertmanager-alerting to the released version
• label-policy.yml — syncs labels and auto-labels PRs based on changed files and branch name
• pr-title.yml — enforces semantic PR title format
• labeler.yml + labels.json — label definitions and auto-label rules

What's Not Included

---

Testing

How Was This Tested?

Test Coverage

• Unit tests added or updated
• Integration tests added or updated
• Manually tested end-to-end

---

Breaking Changes

Does this PR introduce breaking changes?

• Yes
• No

If yes, describe the impact and any required migration steps:

---

Security Considerations

• This PR affects authentication or authorization logic
• This PR touches secrets, tokens, or environment variables
• This PR affects infrastructure, deployment pipelines, or network configuration

If any box is checked, describe the security impact and any mitigations applied:

---

Documentation

Does this PR require documentation updates?

• Yes
• No

If yes, check all that apply:

• README.md
• ARCHITECTURE.md
• API reference
• Architecture diagrams (C4 / DDD)
• /docs

---

UI/UX (If Applicable)

• Includes new components or views
• Changes styles or theme tokens
• Responsive behavior verified
• Requires design approval

Screenshots or recordings:

---

Pre-Merge Checklist

• PR title follows semantic format (feat:, fix:, chore:, docs:, refactor:, test:)
• All CI checks passing
• Code follows project style guidelines
• No debug logs or commented-out code left in
• Dependencies reviewed (no unnecessary additions)
• No sensitive information included

---

Reviewer Notes