chore: update CHANGELOG for audit log retention policy (#950)

Author: msukkari

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 - Added MCP and API key usage tracking to analytics dashboard. Move audit events from client-side to service functions to capture all API calls (web UI, MCP, and non-MCP). Display MCP requests and API requests on separate charts. [#948](https://github.com/sourcebot-dev/sourcebot/pull/948)
+- Added audit log retention policy with `SOURCEBOT_EE_AUDIT_RETENTION_DAYS` environment variable (default 180 days). Daily background job prunes old audit records. [#950](https://github.com/sourcebot-dev/sourcebot/pull/950)
 
 ### Fixed
 - Fixed search query parser rejecting parenthesized regex alternation in filter values (e.g. `file:(test|spec)`, `-file:(test|spec)`). [#946](https://github.com/sourcebot-dev/sourcebot/pull/946)