🧹 [Code Health] Extract SpecializedModuleBackend duplication

[edithatogo]

🎯 What: SpecializedModuleBackend was an exact duplicate of OptionalModuleBackend.
💡 Why: Reduces duplicate code and improves maintainability by subclassing the base class.
✅ Verification: Verified by running tests and pre-commit checks.
✨ Result: Removed 18 lines of duplicate code.

---

PR created automatically by Jules for task 16894287859711778017 started by @edithatogo

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

New to Jules? Learn more at jules.google/docs.

---

For security, I will only act on instructions from the user who triggered this task.

[cursor]

Bugbot is not enabled for your account, so this pull request was not reviewed.

Enable Bugbot in the Cursor dashboard to get automatic reviews on future PRs.

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[github-actions]

🎉 Welcome @edithatogo! Thank you for your first pull request to mars! We're excited to have you as a contributor. Our team will review your PR soon. In the meantime, please ensure all CI checks pass.