ENG-4569 Update backend to make audit query send to ClickHouse based on configuration

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Greptile Overview

Greptile Summary

This PR fixes a bug where the CLICKHOUSE_AUDIT_LOG_INSERT_SETTINGS environment variable defaults were not being applied correctly. Previously, when using Zod's .default() with a .transform(), the default value wasn't used when the environment variable was empty or unset, causing the transformation to return incorrect default values.

Key Changes:

• Extracted DEFAULT_CLICKHOUSE_AUDIT_LOG_INSERT_SETTINGS as a constant at module level
• Changed .default() to use JSON.stringify() of the constant, ensuring the default is applied after transformation
• Changed ClickHouse audit log insert to use auditLog.createdAt from PostgreSQL instead of new Date(), ensuring timestamp consistency between both databases for easier deduplication
• Added explanatory comments for both id and createdAt synchronization

Technical Context:
When Zod's .transform() is applied before .default(), the transformation runs first even for undefined/empty values, so the inline object literal default was never used. By extracting to a constant and using JSON.stringify() in the default, the chain now works correctly: empty values are caught by the transformation, which returns the constant, and the stringified constant serves as the actual default value.

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• The changes are well-focused bug fixes that improve data consistency. The refactoring extracts defaults to a constant (better maintainability), and using auditLog.createdAt from PostgreSQL ensures timestamps match between databases. Both changes are backwards-compatible and don't introduce breaking changes.
• No files require special attention

Important Files Changed

_{Last reviewed commit: 00853fe}