fix(i18n): add pnpm and Node.js setup steps

pnpm is not pre-installed on GitHub ubuntu runners.
Add pnpm/action-setup and setup-node before Claude Code action.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.github/workflows/translate-i18n-claude.yml

@@ -46,6 +46,19 @@ jobs:
           git config --global user.name "github-actions[bot]"
           git config --global user.email "github-actions[bot]@users.noreply.github.com"
 
+      - name: Install pnpm
+        uses: pnpm/action-setup@v4
+        with:
+          package_json_file: web/package.json
+          run_install: false
+
+      - name: Set up Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 'lts/*'
+          cache: pnpm
+          cache-dependency-path: ./web/pnpm-lock.yaml
+
       - name: Detect changed files and generate diff
         id: detect_changes
         run: |