Build: Add USB boot + NVMe HAT support

- --target flag in build.sh (sd|usb|nvme)
- NVMe kernel driver enabled for --target nvme
- EEPROM boot-order config in first-boot wizard
- USB/NVMe flashing docs in build/README.md
- Hardware compatibility + user manual docs from P7

build/first-boot/setup-wizard.sh

@@ -307,6 +307,36 @@ fi
 
 press_enter
 
+# ─── 7. Boot target (USB / NVMe) ──────────────────────────────────────────────
+
+header "Boot Configuration"
+
+echo "This image can boot from SD card, USB SSD, or NVMe HAT."
+echo ""
+
+if [[ -f /sys/kernel/debug/rpi-eeprom/config ]]; then
+    current_order=$(grep BOOT_ORDER /sys/kernel/debug/rpi-eeprom/config 2>/dev/null || echo "unknown")
+    echo "Current boot order: $current_order"
+    echo ""
+    
+    if confirm "Switch to USB boot? (boots USB SSD before SD card)"; then
+        echo "BOOT_ORDER=0xf41" | tee /tmp/eeprom-config.txt
+        sudo rpi-eeprom-config --out /tmp/eeprom-config.bin --config /tmp/eeprom-config.txt
+        echo "USB boot configured. Next boot will try USB first."
+    fi
+    
+    if confirm "Switch to NVMe boot? (boots NVMe before USB and SD)"; then
+        echo "BOOT_ORDER=0xf614" | tee /tmp/eeprom-config.txt
+        sudo rpi-eeprom-config --out /tmp/eeprom-config.bin --config /tmp/eeprom-config.txt
+        echo "NVMe boot configured. Next boot will try NVMe first."
+    fi
+else
+    echo "EEPROM config not accessible. To enable USB/NVMe boot later:"
+    echo "  sudo rpi-eeprom-config --edit"
+    echo "  Set BOOT_ORDER=0xf41 (USB first) or 0xf614 (NVMe first)"
+    echo ""
+fi
+
 # ─── 8. Finalize ─────────────────────────────────────────────────────────────
 
 header "Setup Complete"