fix(packaging): convert dispatch-systemd from user units to system template units (User=%i)

The per-user systemd manager ([email protected]) fails to start on WSL
(kernel 6.6.87.2, microsoft/WSL#13186 — 'Failed to spawn executor:
Device or resource busy'), which breaks pacman's
30-systemd-daemon-reload-user.hook on install.

Changes:
- New [email protected] + [email protected] system
  template units with User=%i (run as the named instance user)
- Remove old user-scope dispatch-api.service / dispatch-frontend.service
- Install to /usr/lib/systemd/system/ instead of .../systemd/user/
- Update PKGBUILD, .install hints, and bin/service to use
  sudo systemctl dispatch-api@<user>

1 files changed, 21 insertions, 0 deletions

diff --git a/packaging/[email protected] b/packaging/[email protected]
new file mode 100644
index 0000000..3449fcb
--- /dev/null
+++ b/packaging/[email protected]
@@ -0,0 +1,21 @@
+# Dispatch API — system service template.
+# Runs under the system manager (PID 1) but drops privileges to the user named
+# in the instance: `dispatch-api@tradam` runs as the `tradam` user.
+#
+# Enable/start:
+#   sudo systemctl enable --now dispatch-api@<user>
+[Unit]
+Description=Dispatch API Backend (running as %i)
+After=network.target
+
+[Service]
+Type=simple
+User=%i
+WorkingDirectory=/opt/dispatch
+ExecStart=/usr/bin/bun packages/api/src/index.ts
+EnvironmentFile=-/etc/dispatch/dispatch-api.conf
+Restart=on-failure
+RestartSec=5
+
+[Install]
+WantedBy=multi-user.target