Fix duplicate-DC-DN crash in --generate-fake-reports (#353)

FakeHealthCheckDataGenerator hardcoded dc.DistinguishedName = "DC=DC"
for every DC in a domain. HeatlcheckRuleAnomalyAuditDC builds a
Dictionary keyed by DistinguishedName and throws on the second .Add()
for any multi-DC domain, causing ~50 crashes per default-population
--generate-fake-reports run (every Medium and Large domain).

Replace the constant with a per-DC unique, properly-formed AD DC DN
that includes the domain FQDN.

Closes #352.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: RockabyeSBJ

PingCastleCommon/Healthcheck/FakeHealthCheckDataGenerator.cs

@@ -469,7 +469,7 @@ private void GenerateComputerData(FakeHealthCheckDataGeneratorDomainModel model,
                 dc.CreationDate = DateBetween2Dates(healthcheckData.DomainCreation, DateTime.Now);
                 // last logon timestam can have a delta of 14 days
                 dc.LastComputerLogonDate = DateTime.Now.AddDays(-1 * rnd.Next(180));
-                dc.DistinguishedName = "DC=DC";
+                dc.DistinguishedName = "CN=" + dc.DCName + ",OU=Domain Controllers,DC=" + healthcheckData.DomainFQDN.Replace(".", ",DC=");
                 dc.OperatingSystem = "Windows 2019";
                 healthcheckData.DomainControllers.Add(dc);
             }