fix(windows): fix encoding issues in PowerShell scripts

- Simplified banner in install.ps1 and ui.ps1 to avoid Unicode box-drawing
  characters that caused parsing errors on some Windows systems
- Fixed PowerShell 5.1 compatibility for ANSI color codes using [char]27
- Renamed Show-Help to Show-InstallerHelp to avoid potential conflicts
- Changed -Help parameter to -ShowHelp for consistency with mole.ps1

windows/lib/core/ui.ps1

@@ -334,19 +334,10 @@ function Show-Banner {
     $cyan = $script:Colors.Cyan
     $nc = $script:Colors.NC
     
-    $banner = @"
-
-  ${purple}███╗   ███╗ ██████╗ ██╗     ███████╗${nc}
-  ${purple}████╗ ████║██╔═══██╗██║     ██╔════╝${nc}
-  ${purple}██╔████╔██║██║   ██║██║     █████╗  ${nc}
-  ${purple}██║╚██╔╝██║██║   ██║██║     ██╔══╝  ${nc}
-  ${purple}██║ ╚═╝ ██║╚██████╔╝███████╗███████╗${nc}
-  ${purple}╚═╝     ╚═╝ ╚═════╝ ╚══════╝╚══════╝${nc}
-  ${cyan}Windows System Maintenance${nc}
-
-"@
-    
-    Write-Host $banner
+    Write-Host ""
+    Write-Host "  ${purple}MOLE${nc}"
+    Write-Host "  ${cyan}Windows System Maintenance${nc}"
+    Write-Host ""
 }
 
 function Show-Header {