feat: add Playwright E2E smoke tests and fix empty namespace crash

Fix getNamespaces() to skip cluster-scoped resources (Namespace: "")
that caused Router.createRouteURL to throw TypeError on the Namespaces
page. Add Playwright E2E smoke tests with Authentik OIDC auth for CI
and K8s token fallback for local dev. Add Gitea Actions E2E workflow,
vitest unit test infrastructure, and test-utils fixtures.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/components/PolarisSettings.test.tsx

@@ -0,0 +1,83 @@
+import { render, screen } from '@testing-library/react';
+import userEvent from '@testing-library/user-event';
+import React from 'react';
+import { describe, expect, it, vi } from 'vitest';
+
+// Mock Headlamp lib
+vi.mock('@kinvolk/headlamp-plugin/lib', () => ({
+  ApiProxy: { request: vi.fn() },
+}));
+
+// Mock Headlamp CommonComponents
+vi.mock('@kinvolk/headlamp-plugin/lib/CommonComponents', () => ({
+  SectionBox: ({ title, children }: { title?: string; children?: React.ReactNode }) => (
+    <div data-testid="section-box" data-title={title}>
+      {children}
+    </div>
+  ),
+  NameValueTable: ({ rows }: { rows: Array<{ name: string; value: React.ReactNode }> }) => (
+    <div data-testid="name-value-table">
+      {rows.map(row => (
+        <div key={row.name}>
+          <span>{row.name}</span>
+          <span>{row.value}</span>
+        </div>
+      ))}
+    </div>
+  ),
+}));
+
+import { setRefreshInterval } from '../api/polaris';
+import PolarisSettings from './PolarisSettings';
+
+describe('PolarisSettings', () => {
+  it('renders with interval from props.data', () => {
+    render(<PolarisSettings data={{ refreshInterval: 60 }} />);
+
+    const select = screen.getByRole('combobox');
+    expect(select).toHaveValue('60');
+  });
+
+  it('falls back to getRefreshInterval when no prop data', () => {
+    // Default is 300 (5 minutes)
+    render(<PolarisSettings />);
+
+    const select = screen.getByRole('combobox');
+    expect(select).toHaveValue('300');
+  });
+
+  it('renders all interval options', () => {
+    render(<PolarisSettings />);
+
+    const options = screen.getAllByRole('option');
+    expect(options).toHaveLength(4);
+    expect(options[0]).toHaveTextContent('1 minute');
+    expect(options[1]).toHaveTextContent('5 minutes');
+    expect(options[2]).toHaveTextContent('10 minutes');
+    expect(options[3]).toHaveTextContent('30 minutes');
+  });
+
+  it('calls setRefreshInterval and onDataChange when selection changes', async () => {
+    const onDataChange = vi.fn();
+    render(<PolarisSettings data={{ refreshInterval: 300 }} onDataChange={onDataChange} />);
+
+    const select = screen.getByRole('combobox');
+    await userEvent.selectOptions(select, '1800');
+
+    // Check localStorage was updated
+    expect(localStorage.getItem('polaris-plugin-refresh-interval')).toBe('1800');
+
+    // Check callback was called with merged data
+    expect(onDataChange).toHaveBeenCalledWith({ refreshInterval: 1800 });
+  });
+
+  it('works without onDataChange callback', async () => {
+    render(<PolarisSettings data={{ refreshInterval: 300 }} />);
+
+    const select = screen.getByRole('combobox');
+    // Should not throw even without onDataChange
+    await userEvent.selectOptions(select, '60');
+
+    expect(localStorage.getItem('polaris-plugin-refresh-interval')).toBe('60');
+  });
+});