feat: Add MaxUSBDrives parameter for parallel USB drive processing

- Introduced a new parameter `MaxUSBDrives` to control the maximum number of USB drives that can be built in parallel, with a default value of 5.
- Updated UI to include a textbox for setting `MaxUSBDrives`.
- Implemented validation to ensure the value is a non-negative integer.
- Adjusted the deployment function to respect the `MaxUSBDrives` limit during USB drive creation.

FFUDevelopment/FFUUI.Core/FFUUI.Core.Handlers.psm1

@@ -44,7 +44,8 @@ function Register-EventHandlers {
         $State.Controls.txtDiskSize,
         $State.Controls.txtMemory,
         $State.Controls.txtProcessors,
-        $State.Controls.txtThreads
+        $State.Controls.txtThreads,
+        $State.Controls.txtMaxUSBDrives
     )
 
     # Attach the handlers to each relevant textbox
@@ -72,6 +73,20 @@ function Register-EventHandlers {
             })
     }
 
+    # Add specific validation for the Max USB Drives textbox to ensure it's an integer >=0 (allow 0 meaning all)
+    if ($null -ne $State.Controls.txtMaxUSBDrives) {
+        $State.Controls.txtMaxUSBDrives.Add_LostFocus({
+                param($eventSource, $routedEventArgs)
+                $textBox = $eventSource
+                $currentValue = 0
+                $isValidInteger = [int]::TryParse($textBox.Text, [ref]$currentValue)
+                if (-not $isValidInteger -or $currentValue -lt 0) {
+                    $textBox.Text = '0'
+                    WriteLog "Max USB Drives value was invalid or less than 0. Reset to 0 (process all)."
+                }
+            })
+    }
+
     # Build Tab Event Handlers
     $State.Controls.btnBrowseFFUDevPath.Add_Click({
             param($eventSource, $routedEventArgs)