nextcloud/user_run: prompt to clean up leftover .bak folders before sync

Before the sync loop, find all *.bak directories in the parent dirs of
configured sync paths, list them with their size, and ask the user to
delete them with a y/N prompt.

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

client_software/0050_nextcloud_desktopclient/user_run.sh

@@ -60,6 +60,29 @@ if [ "${#CLIENT_DATA_SYNC[@]}" -eq 0 ]; then
     exit 0
 fi
 
+#Check for leftover .bak directories from previous failed setups
+_nc_bak_list=$(
+    for CLIENT_DATA_DECLARE_LINE in "${CLIENT_DATA_SYNC[@]}"; do
+        eval "${CLIENT_DATA_DECLARE_LINE}"
+        find "$(dirname "${CLIENT_DATA_SYNC_LINE[0]}")" -maxdepth 1 -type d -name "*.bak" 2>/dev/null
+    done | sort -u
+)
+if [ -n "${_nc_bak_list}" ]; then
+    echo "The following old backup folders were found and should be removed:"
+    echo "${_nc_bak_list}" | while IFS= read -r _nc_d; do
+        [ -n "${_nc_d}" ] && echo "  $(du -sh "${_nc_d}" 2>/dev/null | cut -f1)  ${_nc_d}"
+    done
+    read -r -p "Delete these backup folders? [y/N]: " _nc_del
+    if [ "${_nc_del}" = "y" ] || [ "${_nc_del}" = "Y" ]; then
+        echo "${_nc_bak_list}" | while IFS= read -r _nc_d; do
+            if [ -n "${_nc_d}" ]; then
+                rm -rf "${_nc_d}"
+                echo "Deleted: ${_nc_d}"
+            fi
+        done
+    fi
+fi
+
 #Loop through all Entries
 #_nc_first=1
 _nc_wipe_done=0