Add SQL injection test

[danenania]

Testing feedback links with SQL injection vulnerability

[promptfoo-scanner-staging]

👍 All Clear

This PR adds a test file containing traditional SQL injection code. The security scan examined the changes and found no LLM-related security vulnerabilities, as this code does not involve any AI/LLM functionality.

_{Minimum severity threshold for this scan: 🟡 Medium | Learn more}