Add Drive Wipe boot menu entry and overlay wipe script

Adds a "WIPE ALL DISKS" entry to both GRUB and isolinux menus (bee.wipe=all).
Includes bee-wipe-disks for manual use from a running live system.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

iso/builder/config/bootloaders/isolinux/live.cfg.in

@@ -41,6 +41,12 @@ label live-@FLAVOUR@-failsafe
     initrd @INITRD@
     append @APPEND_LIVE@ nomodeset bee.nvidia.mode=gsp-off noapic noapm nodma nomce nolapic nosmp vga=normal net.ifnames=0 biosdevname=0
 
+label wipe-disks
+    menu label *** WIPE ALL DISKS (irreversible!) ***
+    linux @LINUX@
+    initrd @INITRD@
+    append @APPEND_LIVE@ toram nomodeset bee.gui=off bee.wipe=all net.ifnames=0 biosdevname=0
+
 label memtest
     menu label ^Memory Test (memtest86+)
     linux /boot/memtest86+x64.bin