Fix installer confirmation to accept 'y' in addition to 'yes'

Changed confirmation check from exact 'yes' match to regex pattern that accepts:
- y, Y
- yes, Yes, YES
- Any case variation

This prevents user frustration when typing 'y' instead of full 'yes'.

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

modules/backup/acronis-install.sh

@@ -215,7 +215,7 @@ echo ""
 echo -n "Proceed with installation? (yes/no): "
 read -r confirm
 
-if [ "$confirm" != "yes" ]; then
+if [[ ! "$confirm" =~ ^[Yy]([Ee][Ss])?$ ]]; then
     echo ""
     print_error "Installation cancelled"
     press_enter