feat(audit): archive retention and superseded stale-archive cleanup (ScadaBridge#109)

Owner decisions recorded: the archive destination stays a directory/UNC
(no object-storage client; share + permissions named at enablement),
parquet-tools-only reading (no re-import), unsigned like the chain (#107).

AuditLog:Archive:RetentionDays (default 0 = never delete; else must exceed
AuditLog:RetentionDays, counted from the archived month's end) and
DeleteSupersededStaleArchives (default true) run after every purge tick.
A retried purge's stale Archived archive is deleted only when a later,
verifying, Purged archive of the same partition provably holds every row:
same prior anchor and the stale chain-end hash at its chain-end sequence
(row or tombstone), every unchained row present by EventId; otherwise it is
reported KeptStale. A sole copy left at Archived is never touched. Deletion
removes only the archive name's own three files in its folder, manifest
first, never a manifest-supplied path. `audit archive cleanup [--dry-run]`
= CleanupAuditArchives (Administrator).

AuditLogArchiveCleanupTests (MSSQL) cover retried purge, kept stale copy,
sole copy, retention and the path guard; each safety rule mutation-checked.
Follow-ups filed: #113, #114, #115.

Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV

tests/ZB.MOM.WW.ScadaBridge.ManagementService.Tests/RequiredRoleMatrixTests.cs

@@ -176,6 +176,8 @@ public class RequiredRoleMatrixTests
         // AuditLog Parquet archives (ScadaBridge#42): same audit-read gate as verify-chain.
         ["ListAuditArchives"] = [Roles.Administrator, Roles.Viewer],
         ["VerifyAuditArchive"] = [Roles.Administrator, Roles.Viewer],
+        // Archive cleanup deletes files (ScadaBridge#109): Administrator only.
+        ["CleanupAuditArchives"] = [Roles.Administrator],
 
         // ---- Two-person secured write ----------------------------------------------
         ["SubmitSecuredWrite"] = [Roles.Operator],