fix: disk_usage_check.sh handles inode '-' (vfat/efi), checkdefaults sets target_id

- disk_usage_check.sh: sed 's/-/0/' for filesystems without inodes
- checkdefaults.Ensure: includes target_id in check_defs INSERT so
  signals get proper target slug instead of null

checks/disk_usage_check.sh

@@ -14,7 +14,7 @@ for m in $MOUNTS; do
   PCT=$(echo "$LINE" | awk '{print $3}')
 
   INODE_LINE=$(df -i "$m" 2>/dev/null | awk 'NR==2 {print $5}' | tr -d '%' || echo "0")
-  INODE_PCT="${INODE_LINE:-0}"
+  INODE_PCT=$(echo "${INODE_LINE:-0}" | sed 's/-/0/')
 
   KEY=$(echo "$m" | sed 's|/|_|g' | sed 's|^_||')
   [ -z "$KEY" ] && KEY="root"