🛡️ Sentinel: CRITICAL Fix Hardcoded Default Credentials

[google-labs-jules]

🚨 Severity: CRITICAL
💡 Vulnerability: Hardcoded default credentials and secrets were present in src/main/resources/configuration.properties.
🎯 Impact: If environment variables were not set, the application would start with weak, well-known credentials (root, changeme), allowing unauthorized access to the database and compromising encryption.
🔧 Fix: I removed the default fallback values for DB_USERNAME, DB_PASSWORD, and ENCRYPTION_KEY. The application will now fail to start if these secrets are not provided via environment variables, enforcing a "fail-secure" posture.
✅ Verification: The change was verified by a code review. The build could not be completed due to a private dependency issue that prevented the test suite from running.

---

PR created automatically by Jules for task 16404865368993619770 started by @richkmeli

[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.