fix(systemd): set HOME and DENO_DIR for the systemd service environment

ts/classes/systemd.ts

@@ -25,6 +25,8 @@ Restart=always
 RestartSec=10
 WorkingDirectory=/var/lib/onebox
 Environment=PATH=/usr/bin:/usr/local/bin
+Environment=HOME=/root
+Environment=DENO_DIR=/root/.cache/deno
 
 [Install]
 WantedBy=multi-user.target