🧪 Add tests for generate_savings and refactor script execution block

[lsb11]

🎯 What: The testing gap addressed is the lack of test coverage for the generate_savings function in scripts/generate_apps.py.
📊 Coverage: Tests now cover happy paths (dollar strings with/without plus/commas), error conditions (invalid formats, decimals), and non-dollar strings (e.g. "Free"). The script was also refactored to allow imports without running side effects.
✨ Result: Increased test coverage and validation of data generation scripts logic via the unittest framework.

---

PR created automatically by Jules for task 7320335133645249304 started by @lsb11

[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.

[cloudflare-workers-and-pages]

Deploying stackarchitect2 with    Cloudflare Pages

Latest commit:	bec4880
Status:	✅  Deploy successful!
Preview URL:	https://77c815ee.stackarchitect2.pages.dev
Branch Preview URL:	https://jules-7320335133645249304-43.stackarchitect2.pages.dev

View logs