[Enhancement] Add Graceful Shutdown for All Services #22

Problem

Services partially implement shutdown handlers but not consistently

Impact

• Data may be lost if services are killed abruptly
• Connections not closed properly

Solution

Ensure all services close connections gracefully:

• MongoDB disconnection
• Redis disconnection
• RabbitMQ disconnection
• Pending requests allowed to complete

Acceptance Criteria

• All services implement shutdown handler
• Connections closed in order
• Graceful timeout implemented (30s)
• Tests verify clean shutdown