feat: initialize cart app with blueprints, templates, and CI

Extract cart, order, and orders blueprints with their service layer,
templates, Dockerfile (APP_MODULE=app:app, IMAGE=cart), entrypoint,
and Gitea CI workflow from the coop monolith.

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

.gitea/workflows/ci.yml

@@ -0,0 +1,63 @@
+name: Build and Deploy
+
+on:
+  push:
+    branches: [main]
+
+env:
+  REGISTRY: registry.rose-ash.com:5000
+  IMAGE: cart
+
+jobs:
+  build-and-deploy:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install tools
+        run: |
+          apt-get update && apt-get install -y --no-install-recommends openssh-client
+
+      - name: Set up SSH
+        env:
+          SSH_KEY: ${{ secrets.DEPLOY_SSH_KEY }}
+          DEPLOY_HOST: ${{ secrets.DEPLOY_HOST }}
+        run: |
+          mkdir -p ~/.ssh
+          echo "$SSH_KEY" > ~/.ssh/id_rsa
+          chmod 600 ~/.ssh/id_rsa
+          ssh-keyscan -H "$DEPLOY_HOST" >> ~/.ssh/known_hosts 2>/dev/null || true
+
+      - name: Pull latest code on server
+        env:
+          DEPLOY_HOST: ${{ secrets.DEPLOY_HOST }}
+        run: |
+          ssh "root@$DEPLOY_HOST" "
+            cd /root/cart
+            git fetch origin main
+            git reset --hard origin/main
+          "
+
+      - name: Build and push image
+        env:
+          DEPLOY_HOST: ${{ secrets.DEPLOY_HOST }}
+        run: |
+          ssh "root@$DEPLOY_HOST" "
+            cd /root/cart
+            docker build --build-arg CACHEBUST=\$(date +%s) -t ${{ env.REGISTRY }}/${{ env.IMAGE }}:latest -t ${{ env.REGISTRY }}/${{ env.IMAGE }}:${{ github.sha }} .
+            docker push ${{ env.REGISTRY }}/${{ env.IMAGE }}:latest
+            docker push ${{ env.REGISTRY }}/${{ env.IMAGE }}:${{ github.sha }}
+          "
+
+      - name: Deploy stack
+        env:
+          DEPLOY_HOST: ${{ secrets.DEPLOY_HOST }}
+        run: |
+          ssh "root@$DEPLOY_HOST" "
+            cd /root/cart
+            source .env
+            docker stack deploy -c docker-compose.yml cart
+            echo 'Waiting for services to update...'
+            sleep 10
+            docker stack services cart
+          "