Enhance invoice and item processing with balance tracking features

- Added `company_id` to `ClientProviderAddress` and `ClientProviderPrograms` for better association.
- Updated `_process_with_discharge` to simplify invoice review by removing redundant parameters.
- Improved `pre_validators` to ensure address validation checks for existence before accessing country.
- Enhanced balance comparison logic in `compare_balances` by tracking consumed quantities.
- Modified `fill_available_balances` to reflect invoice status changes from 'UNPROCESSED' to 'PENDING'.
- Introduced `get_lines_with_balance` method in `ItemService` to fetch invoice lines with available balance.
- Added new API endpoint to retrieve import invoice lines with balance information.
- Updated frontend components to display available balances and improve user experience in invoice selection.

frontend/src/lib/api/dashboard/a76/items.ts

@@ -299,5 +299,52 @@ export const itemsApi = {
             company_id: companyId.toString()
         });
         return api.delete(`/v1/a76/items/${itemId}/?${params.toString()}`);
+    },
+
+    /**
+     * Lista las líneas de una factura de importación con su saldo disponible.
+     * Solo las líneas con has_balance = true tienen mercancía disponible para descarga.
+     *
+     * @param invoiceId  - ID de la factura de importación
+     * @param companyId  - ID de la empresa
+     * @param asOfDate   - Fecha corte opcional (ISO: "YYYY-MM-DD").
+     *                     Pasa la fecha de la factura de exportación para que
+     *                     los consumos futuros no se descuenten del saldo.
+     */
+    listByInvoiceWithBalance: (
+        invoiceId: number,
+        companyId: number,
+        asOfDate?: string
+    ) => {
+        const params = new URLSearchParams({ company_id: companyId.toString() });
+        if (asOfDate) params.append('as_of_date', asOfDate);
+        return api.get<ImportLineWithBalance[]>(
+            `/v1/a76/items/invoice/${invoiceId}/items-with-balance?${params.toString()}`
+        );
     }
 };
+
+export interface ImportLineWithBalance {
+    id: number;
+    line_number: number;
+    // Invoice info
+    invoice_number?: string;
+    invoice_date?: string;
+    invoice_status?: string;
+    // Part / class
+    part_number?: string;
+    class_code?: string;
+    description_spanish?: string;
+    unit_of_measure_code?: string;
+    // Quantities
+    quantity?: number;
+    quantity_returned_temp?: number;
+    quantity_returned?: number;
+    // Balance
+    available_balance: number;
+    has_balance: boolean;
+    // FA / subitem
+    is_subitem?: boolean;
+    contains_subitems?: boolean;
+    subitem_count?: number;
+}