fix(docker): install [sftp] extra so paramiko is in the runtime image

The backend Dockerfile only installed the [sqlcipher] extra, so
paramiko wasn't on the path inside the container. SP25 + SP26's
real-mode SFTP client needs paramiko to connect to the Gainwell
MFT — the scheduler tick surfaced this as
'No module named paramiko' on the very first /api/admin/scheduler/tick
against the dzinesco clearhouse with stub=false.

Install both extras ([sqlcipher,sftp]) in builder and runtime stages.

backend/Dockerfile

@@ -35,7 +35,10 @@ COPY pyproject.toml ./
 # the cached wheel metadata when the name+version matches. See git
 # history on this file for the long version.
 COPY src/ ./src/
-RUN pip wheel --no-cache-dir --wheel-dir /wheels '.[sqlcipher]'
+# Install the sftp extra alongside sqlcipher so the real-mode SFTP
+# client (paramiko) is available inside the container — required by
+# SP25 + SP26 for live Gainwell MFT polling.
+RUN pip wheel --no-cache-dir --wheel-dir /wheels '.[sqlcipher,sftp]'
 
 # ---------- runtime ----------
 FROM python:3.11-slim-bookworm
@@ -53,7 +56,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
 WORKDIR /app
 
 COPY --from=builder /wheels /wheels
-RUN pip install --no-cache-dir --no-index --find-links /wheels 'cyclone[sqlcipher]' \
+RUN pip install --no-cache-dir --no-index --find-links /wheels 'cyclone[sqlcipher,sftp]' \
     && rm -rf /wheels
 
 # NOTE: we deliberately do NOT drop privileges to the `cyclone` user.