refactor: align frontend ownership boundaries

Close audit gaps across API drift, query policy, UI, and tests.

src/shared/lib/display.test.ts

@@ -0,0 +1,24 @@
+import { describe, expect, it } from "vitest";
+import { formatMoney, instrumentLogoUrl } from "./display";
+
+describe("shared display helpers", () => {
+	it("formats decimal strings without financial arithmetic", () => {
+		expect(formatMoney({ value: "-1234567.89", currency: "RUB" })).toBe(
+			"-1 234 567,89 ₽",
+		);
+		expect(formatMoney({ value: "10", currency: "RUB" })).toBe("10 ₽");
+		expect(formatMoney({ value: "0.5", currency: "USD" })).toBe("0,5 USD");
+		expect(formatMoney(null)).toBe("—");
+	});
+
+	it("builds the brand logo url from an upstream file name", () => {
+		expect(instrumentLogoUrl("sber3.png")).toBe(
+			"https://invest-brands.cdn-tinkoff.ru/sber3x160.png",
+		);
+		expect(instrumentLogoUrl(" RU000A0JPNM1.png ")).toBe(
+			"https://invest-brands.cdn-tinkoff.ru/RU000A0JPNM1x160.png",
+		);
+		expect(instrumentLogoUrl(null)).toBeNull();
+		expect(instrumentLogoUrl("  ")).toBeNull();
+	});
+});