refactor(#416): delete old LoginButton, replaced by OAuthButton

LoginButton.tsx and LoginButton.test.tsx removed. The login page now
uses OAuthButton, LoginForm, and AuthDivider from the auth redesign.

Refs #416

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/web/src/components/auth/LoginButton.test.tsx

@@ -1,45 +0,0 @@
-import { describe, it, expect, vi, beforeEach } from "vitest";
-import { render, screen } from "@testing-library/react";
-import userEvent from "@testing-library/user-event";
-import { LoginButton } from "./LoginButton";
-
-const { mockOAuth2 } = vi.hoisted(() => ({
-  mockOAuth2: vi.fn(),
-}));
-
-vi.mock("@/lib/auth-client", () => ({
-  signIn: {
-    oauth2: mockOAuth2,
-  },
-}));
-
-describe("LoginButton", (): void => {
-  beforeEach((): void => {
-    mockOAuth2.mockClear();
-  });
-
-  it("should render sign in button", (): void => {
-    render(<LoginButton />);
-    const button = screen.getByRole("button", { name: /sign in/i });
-    expect(button).toBeInTheDocument();
-  });
-
-  it("should initiate OAuth2 sign-in on click", async (): Promise<void> => {
-    const user = userEvent.setup();
-    render(<LoginButton />);
-
-    const button = screen.getByRole("button", { name: /sign in/i });
-    await user.click(button);
-
-    expect(mockOAuth2).toHaveBeenCalledWith({
-      providerId: "authentik",
-      callbackURL: "/",
-    });
-  });
-
-  it("should have proper styling", (): void => {
-    render(<LoginButton />);
-    const button = screen.getByRole("button", { name: /sign in/i });
-    expect(button).toHaveClass("w-full");
-  });
-});

apps/web/src/components/auth/LoginButton.tsx

@@ -1,18 +0,0 @@
-"use client";
-
-import { Button } from "@mosaic/ui";
-import { signIn } from "@/lib/auth-client";
-
-export function LoginButton(): React.JSX.Element {
-  const handleLogin = (): void => {
-    // Use BetterAuth's genericOAuth client to initiate the OIDC flow.
-    // This POSTs to /auth/sign-in/oauth2 and follows the returned redirect URL.
-    void signIn.oauth2({ providerId: "authentik", callbackURL: "/" });
-  };
-
-  return (
-    <Button variant="primary" onClick={handleLogin} className="w-full">
-      Sign In with Authentik
-    </Button>
-  );
-}