Fix #1002: use org default LoggerSettings for anonymous logs

[RajPabnani03]

Summary

Fixes #1002 — Log__c records created without LoggedBy__c (e.g., logs created by external systems via LogEntryEvent__e platform events) skipped the org-level LoggerSettings__c and fell back to the metadata field default for LogRetentionDate__c (14 days), causing anonymous logs to be purged earlier than the configured retention policy.

In Logger.getUserSettings(Schema.User loggingUser), the org-defaults step was gated on loggingUser.Id != null, so anonymous contexts degenerated to "field default only":

// Before
if (loggingUserSettings == null && loggingUser.Id != null && LoggerSettings__c.getOrgDefaults().Id != null) { ... }

// After
if (loggingUserSettings == null && LoggerSettings__c.getOrgDefaults().Id != null) { ... }

Org defaults are org-wide and don't depend on a user ID, so the documented settings hierarchy — User → Profile → Org → Field Default — now applies consistently for anonymous logs as well. This also fixes the same gap in LogEntryEventHandler (which routes LogEntryEvent__e.LoggedById__c through the same method). The SetupOwnerId reassignment stays guarded on loggingUser.Id != null, since it only applies when a real user context exists.

Adds it_should_use_org_default_settings_when_user_is_null to Logger_Tests, covering a Schema.User with no Id/ProfileId.

Testing

Verified in a scratch org (Enterprise Edition, API v67): full nebula-logger/core deploy succeeded and the complete local Apex suite passed — 1260/1260 tests, 93% org-wide coverage — including the new it_should_use_org_default_settings_when_user_is_null.