fix: revert checkout action to standard syntax, remove setup-node

Node.js is already installed on the host runner.
actions/checkout@v4 auto-resolves from GitHub.

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

.gitea/workflows/ci.yml

@@ -10,7 +10,7 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-      - uses: http://127.0.0.1:3300/actions/checkout@v4
+      - uses: actions/checkout@v4
       - run: npm ci
       - run: npm run lint
 
@@ -18,7 +18,7 @@ jobs:
     runs-on: ubuntu-latest
     needs: lint
     steps:
-      - uses: http://127.0.0.1:3300/actions/checkout@v4
+      - uses: actions/checkout@v4
       - run: npm ci
       - run: npm run build
 
@@ -27,7 +27,7 @@ jobs:
     needs: build
     if: gitea.ref == 'refs/heads/main'
     steps:
-      - uses: http://127.0.0.1:3300/actions/checkout@v4
+      - uses: actions/checkout@v4
       - run: npm ci
       - run: npm run build
       - name: Deploy to production