fix(ci): use pnpm instead of npm for workspace:* dependency support

The frontend uses pnpm workspaces with 'workspace:*' protocol that npm
doesn't support. This updates the workflow to:
- Install pnpm using pnpm/action-setup
- Use pnpm for install, sync-schemas, generate-manifest, and build
- Cache pnpm dependencies using pnpm-lock.yaml

.forgejo/workflows/deploy-frontend.yml

@@ -28,6 +28,7 @@ on:
 
 env:
   NODE_VERSION: '20'
+  PNPM_VERSION: '9'
   SERVER_IP: '91.98.224.44'
   SERVER_USER: 'root'
 
@@ -44,28 +45,33 @@ jobs:
             schemas
           sparse-checkout-cone-mode: false
 
+      - name: Install pnpm
+        uses: https://github.com/pnpm/action-setup@v4
+        with:
+          version: ${{ env.PNPM_VERSION }}
+
       - name: Setup Node.js
         uses: actions/setup-node@v4
         with:
           node-version: ${{ env.NODE_VERSION }}
-          cache: 'npm'
-          cache-dependency-path: frontend/package-lock.json
+          cache: 'pnpm'
+          cache-dependency-path: frontend/pnpm-lock.yaml
 
       - name: Install dependencies
         working-directory: frontend
-        run: npm ci
+        run: pnpm install --frozen-lockfile
 
       - name: Sync LinkML schemas to frontend
         working-directory: frontend
-        run: npm run sync-schemas
+        run: pnpm run sync-schemas
 
       - name: Generate schema manifest
         working-directory: frontend
-        run: npm run generate-manifest
+        run: pnpm run generate-manifest
 
       - name: Build frontend
         working-directory: frontend
-        run: npm run build
+        run: pnpm run build
         env:
           VITE_OXIGRAPH_URL: https://bronhouder.nl