feat: migrate GitHub Actions workflow from yarn to pnpm

- Changed package manager detection from yarn.lock to pnpm-lock.yaml
- Added pnpm/action-setup@v4 step with pnpm v9
- Updated cache keys to use pnpm-lock.yaml instead of yarn.lock
- Maintains npm as fallback if pnpm-lock.yaml is not found

Author: abr4xas

.github/workflows/nextjs.yml

@@ -34,10 +34,10 @@ jobs:
       - name: Detect package manager
         id: detect-package-manager
         run: |
-          if [ -f "${{ github.workspace }}/yarn.lock" ]; then
-            echo "manager=yarn" >> $GITHUB_OUTPUT
+          if [ -f "${{ github.workspace }}/pnpm-lock.yaml" ]; then
+            echo "manager=pnpm" >> $GITHUB_OUTPUT
             echo "command=install" >> $GITHUB_OUTPUT
-            echo "runner=yarn" >> $GITHUB_OUTPUT
+            echo "runner=pnpm" >> $GITHUB_OUTPUT
             exit 0
           elif [ -f "${{ github.workspace }}/package.json" ]; then
             echo "manager=npm" >> $GITHUB_OUTPUT
@@ -48,6 +48,10 @@ 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:
@@ -67,10 +71,10 @@ jobs:
           path: |
             .next/cache
           # Generate a new cache whenever packages or source files change.
-          key: ${{ runner.os }}-nextjs-${{ hashFiles('**/package-lock.json', '**/yarn.lock') }}-${{ hashFiles('**.[jt]s', '**.[jt]sx') }}
+          key: ${{ runner.os }}-nextjs-${{ hashFiles('**/package-lock.json', '**/pnpm-lock.yaml') }}-${{ hashFiles('**.[jt]s', '**.[jt]sx') }}
           # If source files changed but packages didn't, rebuild from a prior cache.
           restore-keys: |
-            ${{ runner.os }}-nextjs-${{ hashFiles('**/package-lock.json', '**/yarn.lock') }}-
+            ${{ runner.os }}-nextjs-${{ hashFiles('**/package-lock.json', '**/pnpm-lock.yaml') }}-
       - name: Install dependencies
         run: ${{ steps.detect-package-manager.outputs.manager }} ${{ steps.detect-package-manager.outputs.command }}
       - name: Build with Next.js