Update boot order configuration for eMMC first, then network

Modify the first-boot script and documentation to set the EEPROM boot order to 0xf21, prioritizing eMMC boot followed by network boot. Adjust network boot settings for faster failure on DHCP timeouts and update related scripts and documentation to reflect these changes. Enhance the rescue script to directly modify EEPROM settings without requiring a chroot into eMMC, streamlining the recovery process for devices stuck in network-only boot. Update relevant documentation to ensure clarity on the new boot order and its implications.

emmc-provisioning/network-boot-initramfs/init

@@ -1,10 +1,11 @@
 #!/bin/sh
 # Init for provisioning initramfs: bring up minimal env and run provisioning-client.sh.
 # PROVISIONING_SERVER can be set via kernel cmdline: provisioning_server=http://10.20.50.1:5000
+# Based on Alpine Linux aarch64 with Python 3 and rpi-eeprom-config.
 
 set -e
-export PATH=/bin:/usr/bin
-export LD_LIBRARY_PATH=/lib
+export PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
+export LD_LIBRARY_PATH=/lib:/usr/lib
 
 echo "=== CM4 provisioning initramfs ==="
 # Revision is set at build time; cat /revision.txt to confirm you have the latest initrd on TFTP
@@ -52,7 +53,7 @@ export PROVISIONING_SERVER
 
 if [ "$RESCUE" -eq 1 ]; then
   echo "=== RESCUE MODE (provisioning_rescue=1) ==="
-  echo "Run /rescue-eeprom.sh to mount eMMC and change boot order (rpi-eeprom-config), then reboot."
+  echo "Run /rescue-eeprom.sh to set EEPROM boot order (runs rpi-eeprom-config directly), then reboot."
   # Ensure shell I/O goes to serial console (some setups drop output otherwise)
   [ -c /dev/console ] && exec </dev/console >/dev/console 2>&1
   exec /bin/sh -i