Add Postgres backup script

scripts/backup.sh runs pg_dump inside the ecosplay-auth-db
container, writes a gzipped, timestamped dump to /backup/
(overridable via BACKUP_DIR), and keeps the latest N dumps
(RETENTION=14 by default).

Only the Postgres volume carries state that isn't reproducible
from code (users, credentials, TOTP secrets, sessions, brute-
force counters), so the rest of the repo is not bundled here.

Intended as a base that can later feed a cron job or be piped
to off-site storage (S3, SFTP, borg).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/backup.sh

@@ -0,0 +1,82 @@
+#!/usr/bin/env bash
+# =============================================================
+# E-Cosplay Keycloak backup
+# -------------------------------------------------------------
+# Dumps the Keycloak Postgres database to /backup/ as a
+# timestamped, gzip-compressed SQL file, then rotates old
+# dumps (keeps the latest N).
+#
+# Usage:
+#   ./scripts/backup.sh                 # default settings
+#   BACKUP_DIR=/mnt/nas RETENTION=30 \
+#     ./scripts/backup.sh               # override via env
+#
+# Suggested cron (daily at 03:15):
+#   15 3 * * *  /var/www/e-auth/scripts/backup.sh >>/var/log/e-auth-backup.log 2>&1
+#
+# Note: the repo itself (compose file, realm JSON, themes,
+# Ansible, sync.sh, etc.) lives in git and does not need to
+# be backed up here. Only the Postgres volume carries state
+# that is not reproducible from code (users, credentials,
+# TOTP secrets, sessions, brute-force counters, ...).
+# =============================================================
+
+set -euo pipefail
+
+BACKUP_DIR=${BACKUP_DIR:-/backup}
+RETENTION=${RETENTION:-14}
+PG_CONTAINER=${PG_CONTAINER:-ecosplay-auth-db}
+PG_USER=${PG_USER:-keycloak}
+PG_DB=${PG_DB:-keycloak}
+
+TS=$(date +%F_%H-%M-%S)
+OUT="${BACKUP_DIR}/keycloak-${TS}.sql.gz"
+
+log() { printf '[backup %s] %s\n' "$(date +%T)" "$*"; }
+fail() { printf '[backup %s] ERROR: %s\n' "$(date +%T)" "$*" >&2; exit 1; }
+
+# -------------------------------------------------------------
+# Pre-flight checks
+# -------------------------------------------------------------
+command -v docker >/dev/null || fail "docker not found in PATH"
+
+if ! docker ps --format '{{.Names}}' | grep -qx "${PG_CONTAINER}"; then
+    fail "container '${PG_CONTAINER}' is not running"
+fi
+
+# -------------------------------------------------------------
+# Dump
+# -------------------------------------------------------------
+log "Preparing ${BACKUP_DIR}"
+mkdir -p "${BACKUP_DIR}"
+chmod 700 "${BACKUP_DIR}"
+
+log "Dumping database '${PG_DB}' from container '${PG_CONTAINER}'"
+if ! docker exec "${PG_CONTAINER}" \
+        pg_dump -U "${PG_USER}" -d "${PG_DB}" \
+        --no-owner --clean --if-exists \
+    | gzip -9 > "${OUT}.part"; then
+    rm -f "${OUT}.part"
+    fail "pg_dump failed"
+fi
+
+mv "${OUT}.part" "${OUT}"
+chmod 600 "${OUT}"
+
+SIZE=$(du -h "${OUT}" | cut -f1)
+log "Wrote ${OUT} (${SIZE})"
+
+# -------------------------------------------------------------
+# Rotate: keep only the latest ${RETENTION} backups
+# -------------------------------------------------------------
+log "Pruning backups older than the last ${RETENTION}"
+cd "${BACKUP_DIR}"
+# shellcheck disable=SC2010
+ls -1t keycloak-*.sql.gz 2>/dev/null \
+    | tail -n +"$((RETENTION + 1))" \
+    | while read -r old; do
+        log "  removing ${old}"
+        rm -f "${old}"
+    done
+
+log "Done."