refactor!: support RUB only (WealthLedger/main#55)

Adopt RUB-only API contract; remove currency cards, selectors,
screener currency filter and multi-currency branches.

BREAKING CHANGE: requires the RUB-only backend contract.

src/features/instrument-details/ui/InstrumentChart/InstrumentChart.vm.ts

@@ -19,7 +19,6 @@ function useInstrumentChartVm(props: InstrumentChartProps) {
 	const average = vm.position?.averagePurchasePrice;
 
 	const averageLine = average && props.priceUnit !== "percent"
-		&& average.currency === vm.candles?.currency
 		? Number(average.value)
 		: null;
 
@@ -47,7 +46,7 @@ function useInstrumentChartVm(props: InstrumentChartProps) {
 			currency:
 				props.priceUnit === "percent"
 					? t("bond.percentOfNominal")
-					: (vm.candles?.currency ?? ""),
+					: "₽",
 		},
 	);