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.

emmc-provisioning/cloud-init/user-data.bootstrap

@@ -0,0 +1,35 @@
+#cloud-config
+# Minimal user-data: download bootstrap.sh from your file server and run it at first boot.
+#
+# 1. Host bootstrap.sh at a URL reachable from the device on first boot (e.g. your
+#    provisioning portal or file server). Example: http://10.20.50.1:5000/files/bootstrap.sh
+# 2. Copy this file to the boot partition as "user-data" (with meta-data and optional network-config).
+# 3. Edit BOOTSTRAP_URL below to match your server (or set it once in the runcmd section).
+
+package_update: true
+package_upgrade: false
+
+packages:
+  - curl
+
+# Ensure SSH is enabled and password auth allowed so you can log in after first boot
+write_files:
+  - path: /etc/ssh/sshd_config.d/99-cloud-init.conf
+    content: |
+      PasswordAuthentication yes
+      PermitRootLogin no
+
+runcmd:
+  - systemctl enable ssh
+  - systemctl start ssh
+  # Download and run bootstrap script (edit URL to match your file server)
+  - |
+    BOOTSTRAP_URL="http://10.20.50.1:5000/files/bootstrap.sh"
+    LOG="/var/log/cloud-init-bootstrap.log"
+    if ! curl -fsSL "$BOOTSTRAP_URL" -o /tmp/bootstrap.sh 2>>"$LOG" || [ ! -s /tmp/bootstrap.sh ]; then
+      echo "$(date -Iseconds) ERROR: Failed to download bootstrap.sh from $BOOTSTRAP_URL (file missing or empty)" >> "$LOG"
+      exit 0
+    fi
+    chmod +x /tmp/bootstrap.sh
+    /tmp/bootstrap.sh
+  - cloud-init single --name cc_final_message