🛡️ Sentinel: [CRITICAL] Prevent Hardcoded Default JWT Secret Fallback in Production

[Amer-alsayed]

🚨 Severity: CRITICAL
💡 Vulnerability: The application was falling back to a hardcoded development JWT secret when the environment variable was missing in production mode, which allows attackers to easily forge valid JWT tokens.
🎯 Impact: Total authentication bypass and complete access to user accounts.
🔧 Fix: Changed the fallback logic in server/src/config.js to instead explicitly throw a critical security error and prevent the server from starting if the secret is missing in production.
✅ Verification: Ensure the server fails securely by starting it in production mode without JWT_SECRET configured, verifying it fails with an error and exits securely.

Documented this learning in .jules/sentinel.md as required.

---

PR created automatically by Jules for task 556661989540465764 started by @Amer-alsayed

[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.