ci: use npm install instead of npm ci to avoid lockfile sync issues

The CI runner resolves @emnapi deps differently than local npm, causing
npm ci to fail regardless of Node version. npm install is more forgiving.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitea/workflows/build.yml

@@ -61,7 +61,7 @@ jobs:
       - name: Build frontend
         run: |
           cd web
-          npm ci
+          npm install
           npm run build
           cp -r dist ../cmd/app/frontend/dist