fix: set HOME=/root for rbenv installs to prevent path mismatch

When running in certain LXC environments (e.g. systems with desktop
packages or non-en locales), the HOME variable may resolve to '/'
instead of '/root'. rbenv installs to $HOME/.rbenv, so if HOME is
wrong it ends up in /.rbenv while all service files and PATH exports
hardcode /root/.rbenv, causing 'env: ruby: No such file or directory'.

Explicitly set HOME=/root for all setup_ruby calls that run as root,
and replace all $HOME/.rbenv references in PATH exports and install
steps with /root/.rbenv literals.

Affected scripts:
- ct/sure.sh + install/sure-install.sh (fixes #14479)
- ct/dawarich.sh + install/dawarich-install.sh
- ct/docuseal.sh + install/docuseal-install.sh

Also add TimeoutStartSec=300 to sure.service so db:prepare on first
start does not get killed by the default 90s systemd timeout.

ct/sure.sh

@@ -64,7 +64,7 @@ EOF
     fi
 
     CLEAN_INSTALL=1 fetch_and_deploy_gh_release "Sure" "we-promise/sure" "tarball" "latest" "/opt/sure"
-    RUBY_VERSION="$(cat /opt/sure/.ruby-version)" RUBY_INSTALL_RAILS=false setup_ruby
+    RUBY_VERSION="$(cat /opt/sure/.ruby-version)" RUBY_INSTALL_RAILS=false HOME=/root setup_ruby
 
     msg_info "Updating Sure"
     source ~/.profile