feat(e2e): consolidate E2E infra + add waitForSidebar (PRI-698) (#42)

* feat(e2e): consolidate E2E test infrastructure + add waitForSidebar (PRI-698)

- Adds e2e/auth.setup.ts, e2e/tns-csi.spec.ts with waitForSidebar helper
- Adds playwright.config.ts, scripts/deploy-e2e-headlamp.sh, scripts/teardown-e2e-headlamp.sh
- Adds .github/workflows/e2e.yaml
- Plugin settings test waits for list before searching

* fix(e2e): add @playwright/test to devDependencies and e2e script (PRI-698)

@playwright/test was missing from devDependencies, causing the
'Install Playwright browsers' step to fail. Added it alongside
the e2e npm script so the reusable workflow can run playwright test.

* fix(e2e): reference @main workflow after .github merge

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

---------

Co-authored-by: Chris Farhood <chris@farhood.org>
Co-authored-by: Paperclip <noreply@paperclip.ing>

.github/workflows/e2e.yaml

@@ -0,0 +1,23 @@
+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