- agreement_discount_setting.ui: product list with UiFloat discount inputs
- contract_discount_setting.ui: same for supply contracts
- get_agreement_discount_items.dspy + Python function
- get_contract_discount_items.dspy + Python function
- save_agreement_discount.dspy: create/update/delete items on discount change
- save_contract_discount.dspy: same for supply contracts
- Updated distribution_agreements_list and supply_contracts_list subtables
