feat(iso): 2.1-2.3 — debug ISO builder with SSH access

Builder setup:
- iso/builder/VERSIONS: pinned Alpine 3.21, Go 1.23.6, NVIDIA 550.54.15
- iso/builder/setup-builder.sh: installs build deps + Go on Alpine VM, verifies packages
- iso/builder/build-debug.sh: compiles audit binary, injects SSH keys, builds ISO
- iso/builder/mkimg.bee_debug.sh: Alpine mkimage profile (all audit packages + dropbear)

SSH access (same Ed25519 key as release signing):
- auto-collects ~/.keys/*.key.pub into authorized_keys at build time
- fallback: user bee / password eeb when no keys available
- bee-sshsetup init.d service: creates bee user, sets password, logs status

Debug overlay:
- bee-network: DHCP on all physical interfaces before SSH/audit
- bee-audit-debug: runs audit on boot, leaves SSH up after
- bee-sshsetup: key/password SSH setup
- motd: shows log paths, re-run command, SSH access info

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

iso/overlay-debug/etc/motd

@@ -0,0 +1,19 @@
+
+  ██████╗ ███████╗███████╗    ██████╗ ███████╗██████╗ ██╗   ██╗ ██████╗
+  ██╔══██╗██╔════╝██╔════╝    ██╔══██╗██╔════╝██╔══██╗██║   ██║██╔════╝
+  ██████╔╝█████╗  █████╗      ██║  ██║█████╗  ██████╔╝██║   ██║██║  ███╗
+  ██╔══██╗██╔══╝  ██╔══╝      ██║  ██║██╔══╝  ██╔══██╗██║   ██║██║   ██║
+  ██████╔╝███████╗███████╗    ██████╔╝███████╗██████╔╝╚██████╔╝╚██████╔╝
+  ╚═════╝ ╚══════╝╚══════╝    ╚═════╝ ╚══════╝╚═════╝  ╚═════╝  ╚═════╝
+
+  Hardware Audit LiveCD — DEBUG MODE
+
+  Audit result:  /var/log/bee-audit.json
+  Audit log:     /var/log/bee-audit.log
+  Network log:   /var/log/bee-network.log
+
+  Re-run audit:  /usr/local/bin/audit --output stdout | less
+  Check package: which dmidecode smartctl nvme ipmitool lspci
+
+  SSH access:    key auth (developers) or bee/eeb (password fallback)
+