feat(sqsdlq-otel): implement Dead Letter Queue and OpenTelemetry tracing

[berkdurmus]

This PR introduces two major features to improve the trace-station API's reliability and observability:

Dead Letter Queue (DLQ) Implementation

• Added DLQ configuration and auto-setup in the SQS service
• Implemented message redriving capability to move failed messages from DLQ back to main queue
• Added new API endpoints to view and manage failed messages
• Added comprehensive documentation in DEAD_LETTER_QUEUE.md
• Configured maximum retry count (default: 3 attempts) before messages move to DLQ

OpenTelemetry Tracing Implementation

• Added complete tracing setup with auto-instrumentation for Node.js libraries
• Implemented custom tracing for SQS operations and trace processing
• Added graceful shutdown for proper tracing cleanup
• Created detailed documentation in OPENTELEMETRY.md
• Fixed TypeScript errors related to deprecated semantic conventions:
  • Replaced SemanticResourceAttributes with individual attribute constants
  • Used proper entry points for stable and incubating attributes

Additional Features

• Added support for mock mode in both features via environment variables:
  • MOCK_SQS=true for local development without AWS
  • MOCK_TRACING=true for local development without an OpenTelemetry collector

These changes enhance the API by improving reliability through better error handling with DLQ and providing observability through distributed tracing.