fc5: install postgresql-client + zstd in runtime image so backup/rollback work

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Dockerfile

@@ -16,12 +16,15 @@ ENV PYTHONUNBUFFERED=1 \
     PIP_NO_CACHE_DIR=1 \
     PIP_DISABLE_PIP_VERSION_CHECK=1
 
-# System deps: ffmpeg (transcode + thumbnails, used in FC-2), unar (archives, FC-2),
-# libpq for psycopg, image libs.
+# System deps: ffmpeg (transcode + thumbnails, FC-2), unar (archives, FC-2),
+# libpq for psycopg, postgresql-client + zstd for FC-5 backup/restore
+# (pg_dump + tar --zstd), image libs.
 RUN apt-get update && apt-get install -y --no-install-recommends \
         ffmpeg \
         unar \
         libpq5 \
+        postgresql-client \
+        zstd \
         libjpeg62-turbo \
         libwebp7 \
         libpng16-16 \