🔒 Fix SQL Injection in MainController.loadMemberInfo

[G30RG3-GJ]

This PR fixes a critical SQL Injection vulnerability in MainController.loadMemberInfo where user input was directly concatenated into the SQL query.

Changes:

1. DatabaseHandler.java:

   • Added execQuery(String query, Object... params) which uses PreparedStatement to safely execute parameterized queries.
   • Fixed DatabaseHandler.class.getClass().getResourceAsStream to DatabaseHandler.class.getResourceAsStream to correctly load tables.xml.
   • Replaced JOptionPane.showMessageDialog with LOGGER.log(Level.ERROR, ...) to prevent HeadlessException in non-GUI environments (like tests).
   • Improved exception logging.

2. MainController.java:

   • Updated loadMemberInfo to use databaseHandler.execQuery("SELECT * FROM MEMBER WHERE id = ?", id) instead of string concatenation.

Validation:

• Verified the fix using a custom reproduction test script (TestSQLInjection.java and run_exploit.sh) which confirmed that the SQL injection is no longer possible (returns 0 rows for malicious input instead of leaking data).
• Verified that DatabaseHandler initializes correctly with the resource loading fix.

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PR created automatically by Jules for task 4537194335454198460 started by @G30RG3-GJ

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