Add aws cdk

[mashharuki]

This pull request introduces several enhancements and updates across multiple files to improve functionality, streamline configurations, and add new features. Key changes include updates to Docker configurations, additions to backend functionality, new CDK project files, and adjustments to existing file structures.

Backend Updates:

• pkgs/backend/Dockerfile: Updated the base image to specify the platform (linux/amd64) for better compatibility.
• pkgs/backend/package.json: Modified the Docker build command to include the platform specification and updated the image name to x402-backend-api.
• pkgs/backend/src/index.ts:
  • Added a health check endpoint (/health) for monitoring backend service status.
  • Corrected a typo in the /download endpoint response (result instead of resulut) and added a debug log for endpoint access.

CDK Project Setup:

• pkgs/cdk/.env.example: Introduced environment variables required for the CDK project, including facilitator URL, network, and private key.
• pkgs/cdk/README.md: Added comprehensive documentation for deploying a remote MCP server using AWS CDK, including setup, deployment, and troubleshooting steps.
• pkgs/cdk/cdk.json: Configured CDK settings, including watch options and context parameters for AWS resource management.
• pkgs/cdk/jest.config.js: Added a Jest configuration file for testing CDK functionality.

File Structure and Configuration:

• biome.json: Updated ignore patterns to exclude cdk.out and bundle.js files.
• package.json: Added a new script for managing CDK (pnpm --filter cdk).
• pkgs/cdk/.gitignore and pkgs/cdk/.npmignore: Added ignore patterns for TypeScript files, CDK staging directories, and generated files. [1] [2]