chore: remove E2E testing infrastructure

- Delete e2e/ directory (auth.setup.ts, sealed-secrets.spec.ts, .auth/.gitkeep)
- Delete playwright.config.ts
- Delete scripts/deploy-e2e-headlamp.sh
- Delete scripts/teardown-e2e-headlamp.sh
- Delete .github/workflows/e2e.yaml
- Remove e2e and e2e:headed scripts from package.json
- Remove @playwright/test dependency from package.json

Context: [PRI-1133](/PRI/issues/PRI-1133) — full E2E purge across org.

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

package.json

@@ -29,8 +29,6 @@
     "format:check": "prettier --check src/",
     "test": "vitest run",
     "test:watch": "vitest",
-    "e2e": "playwright test",
-    "e2e:headed": "playwright test --headed",
     "storybook": "headlamp-plugin storybook",
     "storybook-build": "headlamp-plugin storybook-build",
     "i18n": "headlamp-plugin i18n",
@@ -61,7 +59,6 @@
   },
   "devDependencies": {
     "@headlamp-k8s/eslint-config": "^0.6.0",
-    "@playwright/test": "^1.58.2",
     "@iconify/react": "^6.0.2",
     "@kinvolk/headlamp-plugin": "^0.13.0",
     "@mui/material": "^5.15.14",