chore: switch gitleaks to path allowlist (drop fingerprint ignore)

[JakubMini]

Summary

• Replace the brittle fingerprint-based `.gitleaksignore` entry with a path-based allowlist in a new `.gitleaks.toml`.
• The fingerprint approach broke whenever history was rewritten — that's what failed the post-merge gitleaks run on main after PR feat: sign-firmware action (Ed25519, Phase 1) #7 was squash-merged (`6f4c6ff` no longer reachable, `8a37048` was the new commit).
• The path allowlist stays correct across squash merges, rebases, and force-pushes because it does not reference commit hashes.

Files

• New: `.gitleaks.toml` — extends default rules, allowlists `actions/sign-firmware/tests/dummy_private_key.pem`.
• Removed: `.gitleaksignore` — superseded.

Test plan

• gitleaks job on this PR passes (proves both TOML parses and allowlist works)
• After merge, gitleaks workflow on main runs green

🤖 Generated with Claude Code

🐛 Bug Fixes

Fixed gitleaks configuration breaking after squash merges

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 667f11d9-d391-43ee-a570-4b895b515123

📥 Commits

Reviewing files that changed from the base of the PR and between 8a37048 and d1466f3.

📒 Files selected for processing (2)

• .gitleaks.toml
• .gitleaksignore

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Walkthrough

This change replaces a .gitleaksignore entry with a .gitleaks.toml configuration. The new .gitleaks.toml enables Gitleaks’ default rules (extend.useDefault = true) and adds an allowlist entry for the committed test fixture at actions/sign-firmware/tests/dummy_private_key\.pem. The prior ignore line for that path was removed. The update centralizes secret-scan settings into a TOML configuration file consistent with typical tooling configuration practices and coding standards for explicit allowlisting.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/gitleaks-ignore-after-squash

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