auto_detect_email can fetch from defaults.yaml

lib/install.sh

@@ -433,6 +433,8 @@ function is_email_valid {
 
 function auto_detect_email {
     found_email="${EMAIL:-}"
+    [[ -z "$found_email" ]] && [[ -f /etc/miaou/defaults.yaml ]] && found_email=$(yq '.credential.email' /etc/miaou/defaults.yaml)
+    [[ "$found_email" == 'null' ]] && found_email=''
     if ! is_email_valid "$found_email"; then
         if [[ -f $HOME/.ssh/authorized_keys ]]; then
             while IFS= read -r line; do