🔒 Fix SQL Injection in MainController.loadIssueOperation

[G30RG3-GJ]

This PR fixes a SQL Injection vulnerability in MainController.loadIssueOperation where user input was concatenated directly into SQL queries.

Changes:

• Added issueBook method to src/library/assistant/database/DataHelper.java using PreparedStatement.
• Added unit tests for issueBook in test/library/assistant/database/DataHelperTest.java.
• Updated src/library/assistant/ui/main/MainController.java to call DataHelper.issueBook.

Risk:

• The previous code allowed attackers to manipulate the SQL queries via the book ID or member ID fields.
• The fix prevents this by using parameterized queries.

Verification:

• Ran run_tests.sh to verify DataHelper logic.
• Visually verified MainController changes.

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PR created automatically by Jules for task 7577507732969705026 started by @G30RG3-GJ

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