Add a daily purge tick to SiteCallAuditActor that drops terminal SiteCalls
rows older than the retention window via ISiteCallAuditRepository.PurgeTerminalAsync.
The threshold is computed each tick as UtcNow - RetentionDays so an operator who
lowers RetentionDays sees it on the next purge without a restart. Mirrors
AuditLogPurgeActor's daily cadence + continue-on-error posture: a purge fault is
logged and swallowed so the central singleton stays alive and retries next tick.
The purge timer is started in PreStart alongside the reconciliation timer and
gates on the same collaborators (pull client + enumerator) being available — the
repo-only test ctor injects neither, so neither background timer runs there.
Options: PurgeInterval (default 24h, clamped >= 1 min so a zero config value
can't spin the scheduler) + RetentionDays (default 365), plus a test-only
override that bypasses the clamp for millisecond cadences.
Tests (all in-memory, no live MSSQL): purge tick calls PurgeTerminalAsync with a
UtcNow - RetentionDays threshold (non-default 30 days); default retention yields
a 365-day threshold; a throwing repo does not kill the singleton (a second tick
still arrives).
Joseph Doherty
e675b34500