Prepared Statements Lab (Starter)

This is the starter project. Your tasks:

1. Use PreparedStatement for all SQL operations in TransactionService.
2. Implement a transfer that uses a single transaction. On any error, rollback.
3. Add a forced error path (parameter triggerError) to simulate failure and verify rollback.
4. Print simple logs (System.out.println(...)) for: starting tx, executing SQL, commit, rollback.

Run tests: gradle -q test