feat: add Playwright E2E smoke tests

Adds Playwright E2E smoke tests following the headlamp-polaris-plugin
pattern. Tests target a dedicated Headlamp instance in the
privilegedescalation-dev namespace.

- playwright.config.ts: Playwright configuration with auth state
- e2e/auth.setup.ts: OIDC (Authentik) and token-based auth setup
- e2e/intel-gpu.spec.ts: 5 smoke tests covering sidebar, overview,
  device-plugins page, settings, and inter-view navigation
- scripts/deploy-e2e-headlamp.sh: deploys stock Headlamp with plugin
  injected via ConfigMap into privilegedescalation-dev
- scripts/teardown-e2e-headlamp.sh: tears down all E2E resources
- package.json: adds @playwright/test dev dep, e2e/e2e:headed scripts
- .gitignore: excludes auth state, .env.e2e, playwright-report/

Closes #24

Co-Authored-By: Paperclip <noreply@paperclip.ing>

playwright.config.ts

@@ -0,0 +1,27 @@
+import { defineConfig, devices } from '@playwright/test';
+
+export default defineConfig({
+  testDir: './e2e',
+  timeout: 30_000,
+  expect: { timeout: 10_000 },
+  fullyParallel: false,
+  forbidOnly: !!process.env.CI,
+  retries: process.env.CI ? 1 : 0,
+  reporter: 'list',
+  use: {
+    baseURL: process.env.HEADLAMP_URL || 'https://headlamp.animaniacs.farh.net',
+    trace: 'on-first-retry',
+    screenshot: 'only-on-failure',
+  },
+  projects: [
+    { name: 'setup', testMatch: /auth\.setup\.ts/, timeout: 60_000 },
+    {
+      name: 'chromium',
+      use: {
+        ...devices['Desktop Chrome'],
+        storageState: 'e2e/.auth/state.json',
+      },
+      dependencies: ['setup'],
+    },
+  ],
+});