feat(health): AuditRedactionFailure counter + bridge (#23 M5)

Bundle C task M5-T7 — surface DefaultAuditPayloadFilter redactor
over-redactions as a Site Health metric so a misconfigured /
catastrophic regex shows up on /monitoring/health rather than
disappearing into a NoOp sink.

  - SiteHealthReport: new 'AuditRedactionFailure' int field
    (defaulted to 0 for back-compat with existing producers/tests).
  - ISiteHealthCollector / SiteHealthCollector:
    new IncrementAuditRedactionFailure() — per-interval atomic
    counter with Interlocked, reset on CollectReport, mirroring
    the M2 Bundle G SiteAuditWriteFailures pattern.
  - HealthMetricsAuditRedactionFailureCounter: new bridge in
    ScadaLink.AuditLog.Site that forwards IAuditRedactionFailureCounter
    increments to ISiteHealthCollector — mirrors
    HealthMetricsAuditWriteFailureCounter one-for-one.
  - AddAuditLogHealthMetricsBridge: now ALSO Replaces the
    NoOpAuditRedactionFailureCounter binding with the health-metrics
    bridge, so a single AddAuditLogHealthMetricsBridge() call wires
    both the M2 Bundle G write-failure counter and the M5 Bundle C
    redaction-failure counter into the health report.

Site-side only for M5 — the filter also runs on CentralAuditWriter
and AuditLogIngestActor (where it just keeps the NoOp default), but
a central-side health-metric surface for AuditRedactionFailure is
deferred to M6 alongside the rest of the central health collector
work.

Tests:
  - AuditRedactionFailureMetricTests (HealthMonitoring) covers the
    SiteHealthCollector increment/report/reset shape (3 tests).
  - HealthMetricsAuditRedactionFailureCounterTests (AuditLog) covers
    the AuditLog → HealthMonitoring bridge (3 tests).
  - Existing CountCapturingHealthCollector stub in
    DeploymentManagerRedeployTests extended with the new no-op
    interface method.

Verified: dotnet build clean, all 24 test projects green
(the only Failed at first ScadaLink.SiteRuntime.Tests run was the
known-flaky InstanceActorChildAttributeRaceTests; passes on re-run
in isolation and full suite, unrelated to these changes).

src/ScadaLink.Commons/Messages/Health/SiteHealthReport.cs

@@ -25,7 +25,14 @@ public record SiteHealthReport(
     // primary failures (SQLite throws routed to the drop-oldest ring). Surfaces
     // a sustained audit-write outage on /monitoring/health. Defaults to 0 so
     // existing producers / tests that don't construct the field stay valid.
-    int SiteAuditWriteFailures = 0);
+    int SiteAuditWriteFailures = 0,
+    // Audit Log (#23) M5 Bundle C: per-interval count of payload-filter
+    // redactor over-redactions (header / body / SQL parameter stages all
+    // throwing → field replaced with the "<redacted: redactor error>"
+    // marker). Surfaces a misconfigured / catastrophic regex on
+    // /monitoring/health. Defaults to 0 for back-compat with existing
+    // producers and tests that don't construct the field.
+    int AuditRedactionFailure = 0);
 
 /// <summary>
 /// Broadcast wrapper used between central nodes to keep per-node