fix: install pnpm before package manager detection

- Moved pnpm installation step before detect-package-manager
- This fixes the cache error when setup-node tries to use pnpm cache
- pnpm must be installed before setup-node can properly configure its cache

Author: abr4xas

.github/workflows/nextjs.yml

@@ -31,6 +31,10 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v4
+      - name: Install pnpm
+        uses: pnpm/action-setup@v4
+        with:
+          version: 9
       - name: Detect package manager
         id: detect-package-manager
         run: |
@@ -48,10 +52,6 @@ jobs:
             echo "Unable to determine package manager"
             exit 1
           fi
-      - name: Install pnpm
-        uses: pnpm/action-setup@v4
-        with:
-          version: 9
       - name: Setup Node
         uses: actions/setup-node@v4
         with: