Clean up and streamline messy Splunk logging implementation

[chrisgroks]

Overview

Clean up the messy Splunk logging - consolidate 3 loggers into 1, reduce log volume from 5-7 entries per operation to 1-2, improve correlation IDs, and standardize data structure.

Current Problems

• Multiple competing loggers (Winston, Bunyan, Custom Splunk)
• Excessive logging (5-7+ entries per operation)
• Inconsistent formats and correlation
• Maintenance burden

Goals

• Remove Winston and Bunyan, keep only Custom Splunk logger
• Reduce to max 2 log entries per operation
• Consistent correlation IDs
• All 51 tests still pass
• 100% coverage maintained

See documentation/SPLUNK_LOGGING_IMPROVEMENT_PLAN.md for details.