Add exportToExcelSupplierPerSheet and exportToExcelGeneral methods to
LogisticApiService, hitting the existing purchase-supplier endpoint with
export=excel / export=excel-all query params and downloading the server
blob response. Replace the client-side Excel generation in
PurchasesPerSupplierTab with calls to these two service methods, and
split the single Export to Excel button into Export to Excel - Supplier
Per Sheet and Export to Excel - General.
ValdiANS