PR AB: complete Phoenix deployment scaffolding (add 3 files referenced by main 4a1f69a) (#32)

Adds webapp-nginx.conf, systemd/currencicombo-orchestrator.service, and install-prune-cron.sh — all three referenced by main's existing install.sh / deploy script / webapp.service / README but missing from the 4a1f69a commit. Byte-identical to PR #31 branch ded7d24.

Closes gap so CT 8604 can boot cleanly.

scripts/deployment/install-prune-cron.sh

@@ -0,0 +1,102 @@
+#!/usr/bin/env bash
+# install-prune-cron.sh — opt-in cron job to prune old deploy backups.
+#
+# Run ONCE as root (or with sudo) after install.sh to enable daily
+# pruning of /var/lib/currencicombo/backups/. The pruner:
+#   - deletes entries older than 30 days
+#   - ALWAYS keeps the newest N backups regardless of age (default 5)
+#
+# No-op on re-run. Opt out by removing /etc/cron.daily/currencicombo-prune-backups.
+
+set -euo pipefail
+
+BACKUP_DIR="${CC_BACKUP_DIR:-/var/lib/currencicombo/backups}"
+RETAIN_DAYS="${CC_BACKUP_RETAIN_DAYS:-30}"
+KEEP_MIN="${CC_BACKUP_KEEP_MIN:-5}"
+CRON_FILE="/etc/cron.daily/currencicombo-prune-backups"
+DRY_RUN=0
+
+while [[ $# -gt 0 ]]; do
+  case "$1" in
+    --dry-run) DRY_RUN=1; shift ;;
+    -h|--help)
+      cat <<'USAGE'
+Usage: sudo ./install-prune-cron.sh [--dry-run]
+
+Env overrides:
+  CC_BACKUP_DIR         (default: /var/lib/currencicombo/backups)
+  CC_BACKUP_RETAIN_DAYS (default: 30)
+  CC_BACKUP_KEEP_MIN    (default: 5)
+USAGE
+      exit 0 ;;
+    *) echo "unknown arg: $1" >&2; exit 2 ;;
+  esac
+done
+
+log()  { printf '[install-prune-cron] %s\n' "$*" >&2; }
+die()  { printf '[install-prune-cron][FATAL] %s\n' "$*" >&2; exit 1; }
+
+[[ "$EUID" -eq 0 ]] || die "must run as root (sudo)"
+
+# The pruner script body. Runs daily via cron.daily.
+# KEEP_MIN is enforced by listing backups newest-first, skipping the
+# first KEEP_MIN, then deleting any remaining entries older than
+# RETAIN_DAYS. This means we always keep at least KEEP_MIN (even if
+# they're all <30 days old), and never delete one of the newest
+# KEEP_MIN (even if it's >30 days old on a dormant host).
+read -r -d '' PRUNER_BODY <<PRUNER || true
+#!/usr/bin/env bash
+# Managed by scripts/deployment/install-prune-cron.sh. Edits overwritten
+# on next install. Opt out by deleting this file.
+set -euo pipefail
+
+BACKUP_DIR="${BACKUP_DIR}"
+RETAIN_DAYS=${RETAIN_DAYS}
+KEEP_MIN=${KEEP_MIN}
+
+[[ -d "\$BACKUP_DIR" ]] || exit 0
+
+cd "\$BACKUP_DIR"
+mapfile -t all < <(find . -mindepth 1 -maxdepth 1 -type d -printf '%T@ %p\n' 2>/dev/null | sort -rn | awk '{print \$2}')
+
+count=\${#all[@]}
+if (( count <= KEEP_MIN )); then
+  logger -t currencicombo-prune "count=\$count <= KEEP_MIN=\$KEEP_MIN; nothing to prune"
+  exit 0
+fi
+
+cutoff=\$(date -d "\$RETAIN_DAYS days ago" +%s)
+deleted=0
+kept=0
+for i in "\${!all[@]}"; do
+  p="\${all[\$i]}"
+  if (( i < KEEP_MIN )); then
+    kept=\$((kept + 1))
+    continue
+  fi
+  mtime=\$(stat -c %Y "\$p" 2>/dev/null || echo 0)
+  if (( mtime < cutoff )); then
+    rm -rf -- "\$p"
+    deleted=\$((deleted + 1))
+  else
+    kept=\$((kept + 1))
+  fi
+done
+logger -t currencicombo-prune "deleted=\$deleted kept=\$kept total_before=\$count"
+PRUNER
+
+if [[ "${DRY_RUN}" -eq 1 ]]; then
+  log "[dry-run] would write ${CRON_FILE} (0755) with pruner targeting ${BACKUP_DIR}, retain ${RETAIN_DAYS}d, keep-min ${KEEP_MIN}"
+  echo "---"
+  echo "${PRUNER_BODY}"
+  echo "---"
+  exit 0
+fi
+
+printf '%s\n' "${PRUNER_BODY}" > "${CRON_FILE}"
+chmod 0755 "${CRON_FILE}"
+chown root:root "${CRON_FILE}"
+
+log "installed ${CRON_FILE} (backups older than ${RETAIN_DAYS}d, keep-min ${KEEP_MIN}, target ${BACKUP_DIR})"
+log "runs daily via /etc/cron.daily/. Opt out: sudo rm ${CRON_FILE}"
+log "logs to syslog (tag currencicombo-prune); journalctl -t currencicombo-prune"