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/src/ZB.MOM.WW.Auth.Abstractions/Ldap/LdapContracts.cs

@@ -1,3 +1,5 @@
+using System.Net.Security;
+
 namespace ZB.MOM.WW.Auth.Abstractions.Ldap;
 
 public enum LdapTransport { Ldaps, StartTls, None }
@@ -16,6 +18,16 @@ public sealed record LdapOptions
     public string DisplayNameAttribute { get; init; } = "cn";
     public string GroupAttribute { get; init; } = "memberOf";
     public int ConnectionTimeoutMs { get; init; } = 10_000;
+
+    /// <summary>
+    /// Optional hook to harden (or, in dev, relax) TLS server-certificate validation for the
+    /// <see cref="LdapTransport.Ldaps"/> / <see cref="LdapTransport.StartTls"/> transports. When
+    /// <see langword="null"/> (the default) the LDAP client validates the server certificate against
+    /// the OS trust store — it does <em>not</em> blind-accept. Supply a callback to pin a CA, validate
+    /// the SAN against <see cref="Server"/>, or otherwise tighten validation. This is a code-only seam
+    /// (not bound from configuration) and takes precedence over <see cref="AllowInsecure"/>.
+    /// </summary>
+    public RemoteCertificateValidationCallback? ServerCertificateValidationCallback { get; init; }
 }
 
 public enum LdapAuthFailure { BadCredentials, UserNotFound, AmbiguousUser, GroupLookupFailed, ServiceAccountBindFailed, Disabled }