Add workflow to label new bounty issues

[louiss72]

Closes #174

Summary

• Adds a GitHub Actions workflow that runs when a new issue is opened.
• Applies the bounty label to the newly opened issue using the repository GITHUB_TOKEN.
• Limits workflow permissions to contents: read and issues: write.
• Fixes pre-existing tgui lint/typecheck failures reported by CI so the PR can pass the linter gate.

Validation

• Parsed .github/workflows/label_bounty_issues.yml successfully with Ruby YAML parser.
• Ran tools/build/build.sh --ci lint tgui-test successfully locally:
  • 25 Bun tests passed
  • biome lint tgui passed
  • tsc passed

[louiss72]

For payout if this PR is accepted/merged, I can receive Monero at:

4DSQMNzzq46N1z2pZWAVdeA6JvUL9TCB2bnBiA3ZzoqEdYJnMydt5akCa3vtmapeDsbVKGPFdNkzqTcJS8M8oyK7WGjNk99k1B6CoKjvH5

Thanks.

[louiss72]

All required check-runs on 2a3d6a9c are passing now, including linters, map compilation, screenshot comparison, and the integration/alternate test matrix.

The payout address is already included above if this is accepted/merged. Ready for review.