refactor: align frontend ownership boundaries

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

src/test/handlers.ts

@@ -52,6 +52,14 @@ const handlers = [
 			events: [],
 		}),
 	),
+	http.get("*/api/v1/brokerage-accounts/:accountId/income-summary", () =>
+		HttpResponse.json({
+			accountId: "account-1",
+			period: { from: "2026-01-01", to: "2026-08-14" },
+			totalsByCurrency: [],
+			calculatedAt: "2026-08-14T00:00:00Z",
+		}),
+	),
 ];
 
 export { handlers };