Fix all baseline code-review findings across the six shared libraries

Resolves the 35 findings from the 2026-06-01 baseline (commit 26ba1c7),
test-first for every behavioral change. +51 tests (331 -> 382 passing, 0 failed).

- Telemetry-001 (HIGH): RedactionEnricher now honours property removal, so a
  redactor that drops a key actually scrubs the secret from the event.
- Auth: LDAP validator ValidateOnStart; API-key verify no longer fails on a
  best-effort MarkUsed write or a corrupt scopes column (fail-closed); LDAP cert
  validation hook; KeyPrefix persistence aligned; README algorithm corrected.
- Health: Akka checks return Degraded (not throw) when the cluster isn't up yet;
  GrpcDependencyHealthCheck catch-all; null 'description' rendered; composite
  endpoint builder; XML docs shipped.
- Audit: CompositeAuditWriter no longer re-throws OperationCanceledException;
  TruncatingAuditRedactor over-redact scrubs Target + safe negative max; options
  record; XML docs shipped.
- Configuration: TryAddEnumerable idempotent registration; consistent port
  quoting; strict invariant port parsing; XML docs + README packaged.
- Theme: mobile toggle is now CSS-only (no Bootstrap JS); token/CSS hygiene;
  XML docs on the public parameter surface.

Shared-contract/spec docs updated where the code was the source of truth
(observability service.instance.id, MapZbMetrics, redactor reach). All changes
additive/back-compatible at v0.1.0. code-reviews bookkeeping follows separately.

ZB.MOM.WW.Auth/tests/ZB.MOM.WW.Auth.ApiKeys.Tests/ApiKeyVerifierTests.cs

@@ -212,6 +212,51 @@ public class ApiKeyVerifierTests
         Assert.DoesNotContain(Convert.ToBase64String(hash), identityText, StringComparison.Ordinal);
     }
 
+    // --- Auth-002: a failed best-effort MarkUsedAsync must NOT fail a valid key ---
+
+    [Fact]
+    public async Task VerifyAsync_ValidKey_MarkUsedThrows_StillSucceeds()
+    {
+        // MarkUsedAsync is best-effort "last used" bookkeeping. A transient storage failure
+        // (SQLITE_BUSY, disk full, locked DB) must not turn an otherwise-valid credential into a
+        // failed auth: the decision is already made before the usage write. The verifier's contract
+        // is "the only exception path is cancellation", so a non-cancellation MarkUsedAsync failure
+        // is swallowed and the result is still Succeeded == true.
+        byte[] hash = ApiKeySecretHasher.Hash(Secret, Pepper);
+        var store = new FakeApiKeyStore
+        {
+            Record = BuildRecord(hash),
+            MarkUsedException = new InvalidOperationException("SQLITE_BUSY"),
+        };
+        var verifier = BuildVerifier(store, new FakePepperProvider(Pepper));
+
+        ApiKeyVerification result =
+            await verifier.VerifyAsync(Header(KeyId, Secret), CancellationToken.None);
+
+        Assert.True(result.Succeeded);
+        Assert.Null(result.Failure);
+        Assert.NotNull(result.Identity);
+        Assert.Equal(KeyId, result.Identity!.KeyId);
+        Assert.True(store.MarkUsedCalled);
+    }
+
+    [Fact]
+    public async Task VerifyAsync_MarkUsedThrowsOperationCanceled_Propagates()
+    {
+        // The ONLY exception path is cancellation: an OperationCanceledException from the usage
+        // write (e.g. the request was cancelled mid-write) is honoured and re-thrown, not swallowed.
+        byte[] hash = ApiKeySecretHasher.Hash(Secret, Pepper);
+        var store = new FakeApiKeyStore
+        {
+            Record = BuildRecord(hash),
+            MarkUsedException = new OperationCanceledException(),
+        };
+        var verifier = BuildVerifier(store, new FakePepperProvider(Pepper));
+
+        await Assert.ThrowsAnyAsync<OperationCanceledException>(
+            () => verifier.VerifyAsync(Header(KeyId, Secret), CancellationToken.None));
+    }
+
     // --- Cancellation ---
 
     [Fact]
@@ -253,6 +298,9 @@ public class ApiKeyVerifierTests
         public string? MarkUsedKeyId { get; private set; }
         public DateTimeOffset? MarkUsedWhenUtc { get; private set; }
 
+        /// <summary>When set, <see cref="MarkUsedAsync"/> throws this exception (after recording the call).</summary>
+        public Exception? MarkUsedException { get; set; }
+
         public Task<ApiKeyRecord?> FindByKeyIdAsync(string keyId, CancellationToken ct)
         {
             FindByKeyIdCalled = true;
@@ -267,6 +315,11 @@ public class ApiKeyVerifierTests
             MarkUsedCalled = true;
             MarkUsedKeyId = keyId;
             MarkUsedWhenUtc = whenUtc;
+            if (MarkUsedException is not null)
+            {
+                return Task.FromException(MarkUsedException);
+            }
+
             return Task.CompletedTask;
         }
     }