[Observability] Add structured logging + request tracing across all plugins

[thealphacubicle]

Overview

Add consistent structured logging and request tracing across the CKAN, Socrata,
and ArcGIS plugins. Currently logging is inconsistent across plugins, making it
difficult to diagnose issues in Lambda + CloudWatch during beta and production.

Goals

• Define a standard log schema (request ID, plugin name, tool called,
  response time, status)
• Implement structured logging in all three plugins using a consistent format
• Add request tracing so a single MCP tool call can be traced end-to-end
  through Lambda logs
• Ensure logs are CloudWatch-friendly (JSON format)

Deliverables

• Standard log schema defined and documented
• Structured logging implemented in CKAN plugin
• Structured logging implemented in Socrata plugin
• Structured logging implemented in ArcGIS plugin
• Request tracing added to Lambda handler
• Verified logs appear correctly in CloudWatch for Boston instance