Add bind-mount liveness guard to cron container

DokPloy rm-rf's the host code dir on every redeploy, orphaning the
long-running cron container's ./content and ./.git bind mounts (pinned to
the now-deleted inode). The wiki export then spins forever in fs.mkdir
against the dead directory and never commits.

mount-guard.sh detects a stale mount (directory hard-link count < 2 = a
deleted inode) and re-binds it via docker restart, run every 15 min from
cron and once at the top of export-content-cron.sh as a fast-fail.

scripts/mount-guard.sh

@@ -0,0 +1,38 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# =============================================================================
+# Bind-mount liveness guard for the cron container.
+#
+# DokPloy rm-rf's the host code dir on every redeploy, replacing the inode
+# behind ./content and ./.git. This long-running container keeps its bind mount
+# pinned to the now-deleted inode (mountinfo shows ".../content//deleted"), and
+# operations on it break — notably fs.mkdir(recursive) in the export spins
+# forever on the orphaned directory, never reaching the commit/push.
+#
+# Detection: a live directory always has >= 2 hard links (itself + its parent);
+# a deleted/unlinked inode reports 0. So a link count < 2 means the mount is
+# stale. Re-binding requires a container restart — restart re-resolves the bind
+# source to the current host inode (verified); a plain remount from inside the
+# namespace is not possible.
+#
+# Run periodically from cron, and once at the top of export-content-cron.sh.
+# =============================================================================
+
+is_stale() {
+  local dir="$1" links
+  links=$(stat -c %h "$dir" 2>/dev/null || echo 0)
+  [ "$links" -lt 2 ]
+}
+
+for dir in /app/content /app/.git; do
+  if is_stale "$dir"; then
+    echo "$(date -u +%FT%TZ) STALE mount at $dir (hard-link count < 2) — restarting container to re-bind"
+    docker restart "$(cat /etc/hostname)"
+    # Reached only if the restart did not take effect (e.g. socket error).
+    # Sleep so a successful restart kills us here rather than falling through.
+    sleep 10
+    echo "$(date -u +%FT%TZ) ERROR: restart did not take effect for $dir" >&2
+    exit 1
+  fi
+done