docs: reconcile design docs with shipped code (enums, Sms, per-channel retention, SiteCalls schema, conventions)

PLAN-04 Task 24. Component-Commons: AuditChannel gains SecuredWrite (5), AuditKind full
15-value list (+SecuredWrite*/ReconciliationAbandoned), NotificationType Email/Sms (Teams
evaluated+dropped), AuditLogRow persistence-only-projection deviation note. ConfigDB:
Type discriminator Email/Sms, data-layer conventions (UTC DateTime + Utc converter, MSSQL-
only repos/fixtures, AuditLog clustered-key + P3/P4/P6 tracked follow-ups). SiteCallAudit:
schema table rewritten to shipped columns (Channel/Target/AuditStatus-Status/SourceNode/
HttpStatus/IngestedAtUtc; no Kind/TargetSummary/provenance) + stored-vs-tracking-view note.
AuditLog: per-channel retention config lists all 5 channels incl SecuredWrite. Also fixed
two stale 'Teams planned' refs surfaced by the verification grep (HighLevelReqs, CentralUI).

docs/requirements/Component-AuditLog.md

@@ -452,7 +452,8 @@ MS SQL for direct-write events). Unredacted secrets never persist.
   `UX_AuditLog_EventId` until a later tick's CATCH branch rebuilt it.
 - **Per-channel retention overrides (M5.5 T3):** `AuditLog:PerChannelRetentionDays`
   is a dictionary keyed by canonical channel name (`ApiOutbound`, `DbOutbound`,
-  `Notification`, `ApiInbound`) whose value is a retention window in days that
+  `Notification`, `ApiInbound`, `SecuredWrite` — all five `AuditChannel` values are
+  accepted by the validator) whose value is a retention window in days that
   MUST be strictly shorter than the global `RetentionDays`. After the daily
   partition switch-out, the purge actor runs a bounded, batched row DELETE
   (`PurgeChannelOlderThanAsync`) for each channel whose override is shorter than