Improve database resource management and IPC input handling

[RohitKattimani]

Description

This PR addresses a potential resource leak and improves the robustness of the IPC command handling. These changes are non-breaking and maintain the existing simulation logic while improving overall stability.

Changes Made

• Ensured Database Connection Closure: Modified _get_interview_result to use a finally block for conn.close(). This ensures that the database connection is always released, even if json.loads or a cursor operation throws an exception, preventing silent file descriptor leaks.
• Defensive Dictionary Access: Added a default value of 0 when retrieving agent_id in handle_batch_interview. This standardizes behavior with the existing handle_interview method and prevents potential NoneType errors if a command is sent with a missing key.

Testing

• Confirmed that the database still correctly retrieves and parses JSON results for interviews.
• Verified that batch interview commands process correctly even if optional fields are missing.