v0.106.0: offsite provisioning SLICE 2 — controller apply-bridge

On startup reconcile the hub-served offsite: descriptor into a key-only offbox
target. internal/offsiteapply.Bridge: verify-pin box host key vs host_fingerprint
(NO blind TOFU) → consume the one-time password (single-use, never logged) →
sshpass ssh-copy-id -s -f install + verify → configure offbox → EscrowState=pending
(fork-4 via Manager.ApplyOffsiteTarget) → persist a descriptor-hash marker LAST.
Idempotent + fail-safe. Seams faked in tests; both red-proofs run+reverted.
Dockerfile + sshpass. NOT yet live-applied (supervised end-to-end next runbook).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PSK5g6qYLknKj8u3QAFEr6

controller/Dockerfile

@@ -50,7 +50,9 @@ FROM debian:bookworm-slim
 # - rsync: for data migration between storage paths
 # - parted: partprobe (partition table re-read after sfdisk)
 # - restic: encrypted off-box (NAS) backup over SFTP (Part B; version pinned by the Debian release)
-# - openssh-client: restic's sftp backend shells out to `ssh` (the SFTP transport)
+# - openssh-client: restic's sftp backend shells out to `ssh` (the SFTP transport); also ssh-copy-id/sftp
+#   for the SLICE-2 offsite apply-bridge key install
+# - sshpass: feeds the one-time storage-box password to ssh-copy-id -s -f (offsite apply-bridge)
 RUN apt-get update && apt-get install -y --no-install-recommends \
     ca-certificates \
     curl \
@@ -66,6 +68,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     parted \
     restic \
     openssh-client \
+    sshpass \
     && rm -rf /var/lib/apt/lists/*
 
 # Install docker-cli (without daemon)