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>

.github/workflows/e2e.yaml

@@ -1,23 +0,0 @@
-name: E2E Tests
-
-on:
-  push:
-    branches: [main]
-  pull_request:
-    branches: [main]
-  workflow_dispatch:
-
-permissions:
-  contents: read
-
-concurrency:
-  group: e2e-${{ github.repository }}
-  cancel-in-progress: false
-
-jobs:
-  e2e:
-    uses: privilegedescalation/.github/.github/workflows/plugin-e2e.yaml@main
-    with:
-      node-version: "22"
-      headlamp-version: v0.40.1
-      e2e-namespace: headlamp-dev