[Purchase Order Activity]: Add activity tracker

This is to track the activity of purchase, like;

- When was the order created
- Who created the order
- When was the order confirmed
- And, When was the order received

Currently to be discussed

Start by locating where PurchaseOrder data is defined (model/entity and schema/migrations) and where create/confirm/receive actions are processed in code. Also search for any existing activity or audit trail pattern that can store lifecycle metadata. Run the purchase-order test coverage around order state changes after making changes, and treat the issue as done only when creator/confirmation/receipt actors and timestamps are captured consistently for each order lifecycle step.

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