PR #114 pointed the edge-alloy.service unit at /usr/bin/alloy, but the Arch
`grafana-alloy` package installs the binary as /usr/bin/grafana-alloy. The
unit crash-looped with status=203/EXEC ("Unable to locate executable
/usr/bin/alloy"). Make the path a variable (edge_alloy_bin) and default it to
the real path. Verified on edge-1: the binary runs (v1.13.2), the alloy user
exists (in systemd-journal), and the deployed config parses cleanly — only
the ExecStart path was wrong.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>