Fix CI: replace yarn with npm, add package-lock.json

The CI runner does not have yarn installed. Switch to npm install
and npm run build. Also add package-lock.json for reproducible
installs and exclude it from the release ZIP.

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

.gitea/workflows/release.yml

@@ -52,10 +52,10 @@ jobs:
           echo "Building version: $VERSION"
 
       - name: Install Node dependencies
-        run: yarn install --frozen-lockfile
+        run: npm install
 
       - name: Build assets
-        run: yarn build
+        run: npm run build
 
       - name: Validate composer.json
         run: composer validate --no-check-lock --no-check-all
@@ -112,6 +112,7 @@ jobs:
             -x "${THEME_NAME}/node_modules/*" \
             -x "${THEME_NAME}/src/*" \
             -x "${THEME_NAME}/package.json" \
+            -x "${THEME_NAME}/package-lock.json" \
             -x "${THEME_NAME}/yarn.lock" \
             -x "${THEME_NAME}/composer.json" \
             -x "${THEME_NAME}/composer.lock" \