Add winget repair helper and remove winget configure --enable prerequisite

Initialize-Winget.ps1 refreshes PATH, re-registers App Installer and
falls back to the provisioned package before exiting with a Store link.
All scripts that call winget now dot-source this helper instead of
failing on a missing winget.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

powershell/Install-Firefox.ps1

@@ -9,6 +9,8 @@ param(
 
 $ErrorActionPreference = "Stop"
 
+. (Join-Path $PSScriptRoot "Initialize-Winget.ps1")
+
 $IsAdministrator = ([Security.Principal.WindowsPrincipal] [Security.Principal.WindowsIdentity]::GetCurrent()).IsInRole(
     [Security.Principal.WindowsBuiltInRole]::Administrator
 )
@@ -23,10 +25,7 @@ function Install-FirefoxEsr {
         [string]$PackageId
     )
 
-    if (-not (Get-Command winget -ErrorAction SilentlyContinue)) {
-        Write-Error "winget was not found. Install App Installer or enable winget before running this script."
-        exit 1
-    }
+    Initialize-Winget
 
     Write-Host "Installing Firefox ESR with winget: $PackageId" -ForegroundColor Cyan