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/builder/mkimg.bee_debug.sh

@@ -0,0 +1,60 @@
+#!/bin/sh
+# Alpine mkimage profile: bee_debug
+# Minimal LiveCD with audit binary + SSH for development/testing.
+# No NVIDIA driver. SSH root login enabled.
+
+profile_bee_debug() {
+    title="Bee Hardware Audit (debug)"
+    desc="Hardware audit LiveCD with SSH access for testing"
+    image_ext="iso"
+    output_format="iso"
+    kernel_flavors="lts"
+    kernel_addons=""
+    syslinux_serial="0 115200"
+    apks="
+        alpine-base
+        linux-lts
+        linux-firmware-none
+
+        dmidecode
+        smartmontools
+        nvme-cli
+        pciutils
+        ipmitool
+        util-linux
+        lsblk
+        e2fsprogs
+        lshw
+
+        dropbear
+        udhcpc
+        openrc
+        qrencode
+        tzdata
+        ca-certificates
+
+        strace
+        procps
+        lsof
+        file
+        less
+        vim
+    "
+
+    # overlay is applied after package install
+    # contains: audit binary, dropbear init, authorized_keys
+}
+
+build_bee_debug() {
+    # copy overlay files into rootfs
+    local overlay="${SRCDIR}/../../overlay-debug"
+    if [ -d "$overlay" ]; then
+        cp -r "${overlay}/." "${ROOTFS}/"
+    fi
+
+    # enable services
+    _bootscript default bee-sshsetup
+    _bootscript default dropbear
+    _bootscript default bee-network
+    _bootscript default bee-audit-debug
+}