Update admin theme/layout and refresh README details.

Align the project baseline with the latest admin interface styling and layout structure while documenting setup and usage updates in README.

apps/web/e2e/auth/login.spec.ts

@@ -0,0 +1,6 @@
+import { expect, test } from "@playwright/test";
+
+test("login page renders", async ({ page }) => {
+  await page.goto("/login");
+  await expect(page.getByRole("heading", { name: "Вход" })).toBeVisible();
+});