feat: add systemd user service and socket units for owlry-core

Add owlry-core.service (Type=simple, restart-on-failure) and
owlry-core.socket (listening on $XDG_RUNTIME_DIR/owlry/owlry.sock)
for socket-activated daemon deployment.

systemd/owlry-core.service

@@ -0,0 +1,14 @@
+[Unit]
+Description=Owlry application launcher daemon
+Documentation=https://somegit.dev/Owlibou/owlry
+After=graphical-session.target
+
+[Service]
+Type=simple
+ExecStart=/usr/bin/owlry-core
+Restart=on-failure
+RestartSec=3
+Environment=RUST_LOG=warn
+
+[Install]
+WantedBy=default.target

systemd/owlry-core.socket

@@ -0,0 +1,9 @@
+[Unit]
+Description=Owlry launcher socket
+
+[Socket]
+ListenStream=%t/owlry/owlry.sock
+DirectoryMode=0700
+
+[Install]
+WantedBy=sockets.target