feat: introduce backend url environment variable

ref: N25B-352

test/components/Logging/useLogs.test.tsx

@@ -6,6 +6,7 @@ import "@testing-library/jest-dom";
 import {type LogRecord, useLogs} from "../../../src/components/Logging/useLogs.ts";
 import {type cell, useCell} from "../../../src/utils/cellStore.ts";
 import { StrictMode } from "react";
+import { API_BASE_URL } from "../../../src/config/api.ts";
 
 jest.mock("../../../src/utils/priorityFiltering.ts", () => ({
   applyPriorityPredicates: jest.fn((_log, preds: any[]) =>
@@ -83,7 +84,7 @@ describe("useLogs (unit)", () => {
     );
     const es = (globalThis as any).__es as MockEventSource;
     expect(es).toBeTruthy();
-    expect(es.url).toBe("http://localhost:8000/logs/stream");
+    expect(es.url).toBe(`${API_BASE_URL}/logs/stream`);
 
     unmount();
     expect(es.close).toHaveBeenCalledTimes(1);