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/usr/local/bin/bee-network.sh

@@ -0,0 +1,36 @@
+#!/bin/sh
+# bee-network.sh — bring up all physical network interfaces via DHCP
+# Unattended: runs silently, logs results, never blocks.
+
+set -e
+
+LOG_PREFIX="bee-network"
+
+log() { echo "[$LOG_PREFIX] $*"; }
+
+# find physical interfaces: exclude lo and virtual (docker/virbr/veth/tun/tap)
+interfaces=$(ip -o link show \
+    | awk -F': ' '{print $2}' \
+    | grep -v '^lo$' \
+    | grep -vE '^(docker|virbr|veth|tun|tap|br-|bond|dummy)' \
+    | sort)
+
+if [ -z "$interfaces" ]; then
+    log "no physical interfaces found"
+    exit 0
+fi
+
+for iface in $interfaces; do
+    log "bringing up $iface"
+    ip link set "$iface" up 2>/dev/null || { log "WARN: could not bring up $iface"; continue; }
+
+    # DHCP: 3 retries, 5s timeout per try, exit without blocking if no offer
+    if udhcpc -i "$iface" -t 3 -T 5 -n -q 2>/dev/null; then
+        IP=$(ip -4 addr show "$iface" | awk '/inet /{print $2}' | head -1)
+        log "OK: $iface got $IP"
+    else
+        log "WARN: $iface — no DHCP offer"
+    fi
+done
+
+log "done"