chore: pin third-party GitHub Actions to commit SHAs (#45)

## Summary

Pin all third-party GitHub Actions to full-length commit SHAs to prevent
supply chain attacks.

Addresses findings from the
[`third-party-action-not-pinned-to-commit-sha`](https://github.com/launchdarkly/semgrep-rules/blob/main/github-actions/third-party-action-not-pinned-to-commit-sha.yml)
Semgrep rule.

## Test plan

- [ ] Verify CI passes with pinned action SHAs

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Low risk: only changes the workflow action reference to a specific
commit, reducing supply-chain risk without altering release logic.
> 
> **Overview**
> Pins the `google-github-actions/release-please-action` used in
`.github/workflows/release-please.yml` from the floating `@v4` tag to a
specific commit SHA (`v4.4.0`) to improve workflow supply-chain
security.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
70e2919. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------

Co-authored-by: Ryan Lamb <4955475+kinyoklion@users.noreply.github.com>

Author: pkaeding

.github/workflows/release-please.yml

@@ -18,7 +18,7 @@ jobs:
       releases_created: ${{ steps.release.outputs.releases_created }}
 
     steps:
-      - uses: google-github-actions/release-please-action@v4
+      - uses: google-github-actions/release-please-action@e4dc86ba9405554aeba3c6bb2d169500e7d3b4ee # v4.4.0
         id: release
         with:
           token: ${{ secrets.GITHUB_TOKEN }}