fix(windows): address code review issues

- Fix openInExplorer to actually execute explorer.exe (was a no-op)
- Load System.Windows.Forms assembly before using Clipboard
- Use Remove-SafeItem in purge for consistent safety checks
- Fix Dropbox typo (was DroplboxCache)

windows/lib/clean/apps.ps1

@@ -207,7 +207,7 @@ function Clear-OneDriveCache {
     }
 }
 
-function Clear-DroplboxCache {
+function Clear-DropboxCache {
     <#
     .SYNOPSIS
         Clean Dropbox cache
@@ -405,7 +405,7 @@ function Invoke-AppCleanup {
     # Productivity apps
     Clear-OfficeCache
     Clear-OneDriveCache
-    Clear-DroplboxCache
+    Clear-DropboxCache
     Clear-GoogleDriveCache
     
     # Creative apps

windows/lib/clean/user.ps1

@@ -289,6 +289,9 @@ function Clear-ClipboardHistory {
     }
     
     try {
+        # Load Windows Forms assembly for clipboard access
+        Add-Type -AssemblyName System.Windows.Forms -ErrorAction SilentlyContinue
+        
         # Clear current clipboard
         [System.Windows.Forms.Clipboard]::Clear()