fix: Remove yarn cache from setup-node to fix yarn not found error

- Remove cache: 'yarn' from setup-node action as yarn isn't available yet
- Corepack will handle yarn installation after Node.js setup
- Fixes error where setup-node tries to use yarn before it's installed

.gitea/workflows/ci.yml

@@ -134,8 +134,6 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: '24'
-          cache: 'yarn'
-          cache-dependency-path: bugulma/frontend/yarn.lock
       - name: Enable Corepack (for Yarn)
         run: corepack enable
       - name: Install dependencies