Warn when disk space is low before updating in Quattro (#6432)

* Warn when disk space is low before updating

* Simplify update free space warning

* Stop updates without enough free space

* Allow forcing updates with low disk space

---------

Co-authored-by: David Heinemeier Hansson <david@hey.com>

bin/omarchy-update-requires-free-space

@@ -0,0 +1,17 @@
+#!/bin/bash
+
+# omarchy:summary=Check free disk space required for an update
+# omarchy:hidden=true
+
+set -e
+
+if [[ ${OMARCHY_UPDATE_FORCE:-0} == "1" ]]; then
+  exit 0
+elif read -r available_bytes < <(df --output=avail --block-size=1 / 2>/dev/null | tail -n 1) &&
+  [[ $available_bytes =~ ^[0-9]+$ ]] &&
+  (( available_bytes < 10 * 1024 * 1024 * 1024 )); then
+  echo "You need at least 10 GiB free to safely update Omarchy."
+  exit 1
+else
+  exit 0
+fi