refactor: reuse FkMultiSelectField for report period/payee selectors

Export FkMultiSelectField from react-openapi and use it directly in the
report viewer for the Period/Payee dimension filters instead of the
custom OptionMultiSelect component, gaining the admin panel's QoL
behavior (no close-on-click, selected-first with tick marks, chips).
Feed it fabricated FieldConfigs plus fkOptions derived from the report's
metadata.group_options; delete the standalone OptionMultiSelect.

react-openapi/index.ts

@@ -6,6 +6,7 @@ export { useResource } from "./src/context/useResource";
 export { ListCellRenderer, DetailFieldRenderer, applyDisplayFormat } from "./src/components/fields";
 export { FormFieldRenderer } from "./src/components/fields/FormFieldRenderer";
 export { CurrencyField, formatCurrency } from "./src/components/fields/renderers/CurrencyField";
+export { FkMultiSelectField } from "./src/components/fields/renderers/FkMultiSelectField";
 export { SseStreamView } from "./src/components/SseStreamView";
 export { SseConnectionStatus } from "./src/components/SseConnectionStatus";
 export { getApi } from "./src/hooks/useApi";