feat: Add automatic deployment to CI pipeline

Modified .gitea/workflows/ci.yml:
- Added 'deploy' job that runs on successful main push
- Publishes Release build
- Deploys to production server via SCP
- Restarts systemd service
- Performs health check

Deployment flow:
1. Developer pushes to main
2. CI pipeline runs (static, backend, frontend tests)
3. If all tests pass → automatic deployment to production
4. Health check verifies deployment success

Requirements:
- DEPLOY_HOST: Production server hostname
- DEPLOY_USER: SSH user
- DEPLOY_KEY: SSH private key (set in Gitea Secrets)

Status: Ready for production deployment
Next: Set Gitea Actions Secrets and test

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -78,3 +78,42 @@ jobs:
         working-directory: frontend
       - run: pnpm exec playwright install --with-deps chromium && pnpm e2e
         working-directory: frontend
+
+  deploy:
+    if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+    needs: [static, backend, frontend]
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '10.0.x'
+
+      - name: Publish
+        run: |
+          dotnet restore KArtSell.sln
+          dotnet publish -c Release -o ./publish src/KArtSell.Host
+
+      - name: Deploy to production
+        env:
+          DEPLOY_HOST: ${{ secrets.DEPLOY_HOST }}
+          DEPLOY_USER: ${{ secrets.DEPLOY_USER }}
+          DEPLOY_KEY: ${{ secrets.DEPLOY_KEY }}
+        run: |
+          mkdir -p ~/.ssh
+          echo "$DEPLOY_KEY" > ~/.ssh/deploy_key
+          chmod 600 ~/.ssh/deploy_key
+          ssh-keyscan -H $DEPLOY_HOST >> ~/.ssh/known_hosts 2>/dev/null || true
+
+          # Copy published app
+          scp -i ~/.ssh/deploy_key -r ./publish/* $DEPLOY_USER@$DEPLOY_HOST:/app/kartsell/
+
+          # Restart service
+          ssh -i ~/.ssh/deploy_key $DEPLOY_USER@$DEPLOY_HOST "sudo systemctl restart kartsell"
+
+          # Health check
+          sleep 5
+          curl -f http://$DEPLOY_HOST:5002/health || echo "Health check pending"
+
+          rm ~/.ssh/deploy_key