## Why

The Bán hàng (POS) customer info panel currently shows a read-only "Người thân" (dependant) field for the selected customer, which has no bearing on the sale in progress. Meanwhile the cashier has no visibility into that customer's outstanding debt (`debt_total`) while deciding how much to grant as "Tiền nợ" on the current order — they'd have to leave the POS screen and look the customer up separately. Since debt data is already fetched with the customer (the `/customers/scan` search endpoint returns the full `Customer` model, `debt_total` included), swapping the low-value dependant display for a debt display is a same-screen, no-new-endpoint change.

## What Changes

- Remove the "Người thân" (`data-model="dependant"`) read-only field from the POS customer info panel (`resources/views/pages/pos.blade.php`).
- Add a "Nợ hiện tại" (current debt) read-only field in its place, bound to the selected customer's `debt_total`.
- The debt field is only shown when the selected customer has `debt_total` greater than 0; it stays hidden for a customer with no debt, and when no customer is selected.
- **Not changing**: the separate "Người thân" input in the "Thêm khách hàng" (add customer) modal on the same page — that field is for entering a new customer's data, not for displaying a selected customer's info, and is out of scope for this change.

## Capabilities

### New Capabilities
*(none)*

### Modified Capabilities
- `pos-debt-entry`: adds a requirement that the POS customer info panel displays the selected customer's current outstanding debt (when greater than zero) at the time of customer selection, ahead of any new "Tiền nợ" entry for the order in progress.

## Impact

- `resources/views/pages/pos.blade.php` — customer info panel: remove the `dependant` form-group, add a `debt_total` form-group.
- `app/Http/Controllers/PosController.php` — inline `Admin::script` block: `fillCustomerInfo()` toggles the new debt field's visibility based on `cus.debt_total`; no AJAX/endpoint change needed since `/customers/scan` (`CustomerController::scan`) already returns the full `Customer` model, including `debt_total`.
- No database or API changes.