controller v0.93.0: NAS Part B off-box backup target (restic-over-SFTP)

Encrypted restic repo over SFTP for the app-data tier (the off-site 3-2-1 leg). A dead
NAS fails fast via -oConnectTimeout (spike Q8), never hangs the runner; secrets are 0600
files (ride DR via PBS whole-CT); init-if-absent, retention forget --prune, restore,
single-flight, per-app toggle + UI. restic re-added to the image.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HxLA1mZurFq9kt8hneFeCs

controller/Dockerfile

@@ -49,6 +49,8 @@ FROM debian:bookworm-slim
 # - e2fsprogs: mkfs.ext4 (filesystem formatting)
 # - 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)
 RUN apt-get update && apt-get install -y --no-install-recommends \
     ca-certificates \
     curl \
@@ -62,6 +64,8 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     e2fsprogs \
     rsync \
     parted \
+    restic \
+    openssh-client \
     && rm -rf /var/lib/apt/lists/*
 
 # Install docker-cli (without daemon)