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.

Test-WeakADPasswords.ps1

@@ -95,7 +95,7 @@ function Invoke-UsageBeacon {
     if ($normalizedMethod -in @('POST', 'PUT')) {
         $payload = [ordered]@{
             script   = 'Test-WeakADPasswords'
-            version  = '2.2.1'
+            version  = $ElysiumVersion
             ranAtUtc = (Get-Date).ToUniversalTime().ToString('o')
         }
         if (-not [string]::IsNullOrWhiteSpace($InstanceId)) {