🛡️ Sentinel: [MEDIUM] Fix missing input validation (division by zero risk)

[CFMVCarlos]

🚨 Severity: MEDIUM
💡 Vulnerability: Missing input validation on user data could lead to unhandled exceptions (ZeroDivisionError) exposing stack traces. Negative values for resistance were also possible.
🎯 Impact: Unhandled exceptions could lead to application crash or information exposure via stack traces.
🔧 Fix: Added explicit input validation in lib/voltage_divider_calculations.py to prevent negative inputs and division by zero. Exceptions are now caught and thrown as safe ValueError with clear messages.
✅ Verification: Ran manual tests against previously failing inputs (e.g. vin=5, vout=5, r1=100) to ensure they raise ValueError as expected.

---

PR created automatically by Jules for task 5776406556588723546 started by @CFMVCarlos

[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.