feat: complete saleor core extensions app with React email templates

- Order confirmation, shipped, and cancelled email templates
- Uses @react-email/components for professional HTML emails
- Sends admin and customer notifications
- Integrates with Resend for email delivery
- Webhook handlers for ORDER_CREATED, ORDER_FULFILLED, ORDER_CANCELLED
- Docker image optimized for production
- Persistent auth data storage via PVC

.devcontainer/Dockerfile

@@ -0,0 +1,15 @@
+FROM mcr.microsoft.com/devcontainers/typescript-node:22
+
+ENV PNPM_HOME="/home/node/.pnpm"
+ENV PATH="$PNPM_HOME:$PATH"
+RUN corepack enable
+
+WORKDIR /app
+
+# This is needed so pnpm-store volume is created with correct permissions (see docker-compose.yml)
+RUN mkdir -p /app/.pnpm-store
+RUN chown -R node:node /app/.pnpm-store
+
+COPY package.json pnpm-lock.yaml ./
+RUN pnpm install --frozen-lockfile
+RUN chown -R node:node /home/node/.pnpm