🔒 Fix SQL Injection in MainController.java

[G30RG3-GJ]

This PR fixes multiple SQL injection vulnerabilities in MainController.java by introducing parameterized query support in DatabaseHandler.java.

Changes:

1. DatabaseHandler.java:
   • Added execAction(String query, Object... params) using PreparedStatement.
   • Added execQuery(String query, Object... params) using PreparedStatement.
   • Fixed inflateDB to correctly load tables.xml resource using DatabaseHandler.class.getResourceAsStream instead of .getClass().getResourceAsStream.
2. MainController.java:
   • Refactored loadSubmissionOp, loadMemberInfo, loadIssueOperation, loadBookInfo2, and loadRenewOp to use the new parameterized methods.
3. Tests:
   • Added test/library/assistant/database/DatabaseHandlerExecTest.java to verify parameterized execution and SQL injection prevention.
   • Added stubs in test/stubs to allow compilation of DatabaseHandler in the headless test environment.

Security Impact:

• Eliminates SQL injection vectors where user input (Book ID, Member ID) was directly concatenated into SQL strings.
• Uses PreparedStatement which treats parameters as literal values, neutralizing injection payloads.

Verification:

• DatabaseHandlerExecTest passes, confirming that execAction works with parameters and that SQL injection attempts (e.g. ' OR '1'='1) are ineffective.

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PR created automatically by Jules for task 6378433451357861885 started by @G30RG3-GJ

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