Enhance apigw-lambda-sns pattern with production-ready improvements

[BigBoss531]

Issue #, if available:

Continuation of this PR - attempted it incorrectly. All comments addressed in this PR

Description of changes:

• Add comprehensive error handling with proper HTTP status codes
• Implement environment variable validation for TOPIC_ARN
• Return structured JSON responses with message IDs
• Update API Gateway integration to aws_proxy type for proper response handling
• Add 400/500 error response mappings in OpenAPI spec
• Upgrade Python runtime from 3.8 to 3.13
• Improve logging with detailed error information
• Added a Canary to monitor the API GW
• Added a CloudWatch Alarm to monitor 5XX errors on APIGW
• Enabled X-Ray Active Tracing on Lambda & APIGW (These can be disabled by end user)

Ive tested and confirmed the above locally in my account via sam deploy

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.