Add Playwright composite action to reduce workflow duplication (#5754)

This PR introduces a reusable composite action for Playwright setup to
reduce duplication across workflows.

## Changes
- Created `.github/actions/setup-playwright/action.yml` composite action
that:
  - Detects or uses provided Playwright version
  - Caches Playwright browsers with intelligent cache keys
  - Installs browsers only when cache miss occurs
  - Installs OS dependencies when cache hit occurs
  
## Technical Details
- **Important:** The composite action requires `shell: bash` for all
`run` steps as per [GitHub Actions requirements for composite
actions](https://docs.github.com/en/actions/creating-actions/creating-a-composite-action#creating-an-action-metadata-file).
This is a mandatory field for composite actions, unlike regular workflow
steps.
- Updated workflow paths to account for repository checkout locations
(some workflows checkout to subdirectories like `ComfyUI_frontend/`)
- Uses conditional caching to avoid redundant browser installations

## Benefits
- Reduces code duplication across 6 workflow files
- Centralizes Playwright caching logic  
- Consistent browser setup across all workflows
- Easier maintenance and updates
- Faster CI runs through intelligent caching

## Affected Workflows
- `.github/workflows/test-ui.yaml` (2 uses)
- `.github/workflows/i18n-custom-nodes.yaml`
- `.github/workflows/i18n-node-defs.yaml`
- `.github/workflows/i18n.yaml`
- `.github/workflows/test-browser-exp.yaml`

---------

Co-authored-by: GitHub Action <action@github.com>

.github/workflows/update-node-definitions-locales.yaml

@@ -13,11 +13,9 @@ jobs:
   update-locales:
     runs-on: ubuntu-latest
     steps:
-    - name: Setup Frontend
-      uses: ./.github/actions/setup-frontend
-    - name: Install Playwright Browsers
-      run: pnpm exec playwright install chromium --with-deps
-      working-directory: ComfyUI_frontend
+    - uses: Comfy-Org/ComfyUI_frontend_setup_action@v3
+    - name: Setup Playwright
+      uses: ./.github/actions/setup-playwright
     - name: Start dev server
       # Run electron dev server as it is a superset of the web dev server
       # We do want electron specific UIs to be translated.