chore: centralize version and add Bump-Version.ps1

- Add  to Elysium.Common.ps1 as the single
  runtime source of truth for version strings.
- Update Update-KHDB.ps1 User-Agent to reference .
- Update Test-WeakADPasswords.ps1 usage beacon payload to reference
  .
- Add Bump-Version.ps1 release helper that updates the centralized
  variable, ASCII headers across .ps1/.py files, runtime references,
  and prints a CHANGELOG stub.

Update-KHDB.ps1

@@ -61,7 +61,7 @@ function New-HttpClient {
     Add-Type -AssemblyName System.Net.Http -ErrorAction SilentlyContinue
     $client = [System.Net.Http.HttpClient]::new()
     $client.Timeout = [TimeSpan]::FromSeconds(600)
-    $client.DefaultRequestHeaders.UserAgent.ParseAdd('Elysium/2.2.1 (+Update-KHDB)')
+    $client.DefaultRequestHeaders.UserAgent.ParseAdd("Elysium/$ElysiumVersion (+Update-KHDB)")
     return $client
 }