## ADDED Requirements

### Requirement: POS customer panel displays the selected customer's current outstanding debt
When a customer is selected on the Bán hàng (POS) screen, the customer info panel SHALL display that customer's current `debt_total` if it is greater than zero. The panel SHALL NOT show a debt line for a customer whose `debt_total` is zero, nor when no customer is selected. This display is read-only and independent of the "Tiền nợ" input for the order currently being entered.

#### Scenario: Selected customer has outstanding debt
- **WHEN** a customer with `debt_total` greater than zero is selected on the POS screen
- **THEN** the customer info panel shows that customer's current debt amount

#### Scenario: Selected customer has no debt
- **WHEN** a customer with `debt_total` equal to zero is selected on the POS screen
- **THEN** the customer info panel shows no debt line for that customer

#### Scenario: No customer selected
- **WHEN** no customer has been selected on the POS screen (including after clearing a previous selection)
- **THEN** the customer info panel shows no debt line

#### Scenario: Debt display is independent of the current order's debt entry
- **WHEN** a customer with existing `debt_total` greater than zero is selected and the seller then enters a new "Tiền nợ" amount for the order in progress
- **THEN** the displayed current-debt amount continues to reflect the customer's `debt_total` as it was at selection time, and is not altered by the in-progress "Tiền nợ" entry until the order is actually completed