Fix SonarCloud python:S6437 — remove hard-coded DB password

[mpchenette]

This PR resolves the open code scanning alert (SonarCloud python:S6437) by removing the hard-coded MySQL credential in python/sql.py and switching to environment-based configuration:

• Added os import and read DB_USER, DB_PASSWORD, DB_HOST, DB_NAME from the environment (with sensible defaults except for password).
• Kept changes minimal per repo guidelines.

Follow-ups suggested (not in this PR):

• Parameterize SQL queries to prevent injection in search_user() and add_user().
• Fix add_user() connection call (mysql.connector.connect(...)).

Please set DB_PASSWORD (and other optional vars) in your environment before running.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud