Refactor golden image handling in backup upload process</message>

<message>Update the _set_golden_from_path function to improve the handling of existing golden image files. Replace the existing unlink logic with a more robust method that safely removes files or broken symlinks using the missing_ok parameter. This change enhances the reliability of the backup upload process by ensuring that stale references are properly cleared before setting a new golden image path.

backup-from-device/gnss-guard/gnss-guard.service

@@ -0,0 +1,19 @@
+[Unit]
+Description=TM GNSS Guard - GPS Spoofing and Jamming Monitor
+After=network.target
+
+[Service]
+Type=simple
+User=pi
+WorkingDirectory=/home/pi/tm-gnss-guard
+ExecStart=/home/pi/tm-gnss-guard/.venv/bin/python /home/pi/tm-gnss-guard/main.py
+Restart=always
+RestartSec=10
+StandardOutput=append:/home/pi/tm-gnss-guard/gnss_guard.log
+StandardError=append:/home/pi/tm-gnss-guard/gnss_guard.log
+
+# Environment
+Environment=PYTHONUNBUFFERED=1
+
+[Install]
+WantedBy=multi-user.target