feat: Add Install-Dependencies.ps1 for SharePoint XLS Converter setup

Install-Dependencies.ps1

@@ -0,0 +1,50 @@
+#Requires -RunAsAdministrator
+<#
+.SYNOPSIS
+Installs prerequisites for SharePoint XLS Converter application
+#>
+
+# Enable TLS 1.2 for secure connections
+[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
+
+Write-Host "Installing required modules..." -ForegroundColor Cyan
+
+# Install PnP.PowerShell module if not exists
+if (-not (Get-Module -ListAvailable -Name PnP.PowerShell)) {
+    try {
+        Install-Module PnP.PowerShell -Scope CurrentUser -Force -AllowClobber
+        Write-Host "PnP.PowerShell module installed successfully" -ForegroundColor Green
+    }
+    catch {
+        Write-Host "Failed to install PnP.PowerShell: $_" -ForegroundColor Red
+        exit 1
+    }
+}
+else {
+    Write-Host "PnP.PowerShell module is already installed" -ForegroundColor Yellow
+}
+
+# Check for Excel installation
+try {
+    $excelCheck = New-Object -ComObject Excel.Application -ErrorAction Stop
+    $excelCheck.Quit()
+    [System.Runtime.Interopservices.Marshal]::ReleaseComObject($excelCheck) | Out-Null
+    Write-Host "Microsoft Excel is installed" -ForegroundColor Green
+}
+catch {
+    Write-Host @"
+    Microsoft Excel not found! The conversion feature requires:
+    1. Microsoft Excel 2013 or newer
+    2. PowerShell must run in STA mode
+    Run the main script like this:
+    powershell.exe -STA -File .\MainForm.ps1
+"@ -ForegroundColor Red
+    exit 1
+}
+
+Write-Host @"
+Installation complete! Run the main application with:
+powershell.exe -STA -File .\MainForm.ps1
+
+Note: First run might take longer while modules load
+"@ -ForegroundColor Green