Add conf_cache_watchdog.sh — watchdog-driven persistent conf backup

Writes partner confs from RAM cache to /boot/config/.cache/vv/d/ while
remote is offline, and removes the backup when remote comes back. Called
each minute via SYSTEM_WATCHDOG_SCRIPTS so crashes and power loss are
covered — not just graceful shutdowns.

Watchdogs/System/conf_cache_watchdog.sh

@@ -0,0 +1,69 @@
+#!/bin/bash
+# ==============================================================================================
+# ============================= Conf Cache Watchdog ============================================
+# ==============================================================================================
+#
+# PURPOSE
+# ─────────────────────────────────────────────────────────────────────────────
+# Maintains the persistent partner conf backup at /boot/config/.cache/vv/d/.
+# Runs every minute via SYSTEM_WATCHDOG_SCRIPTS.
+#
+# When remote is OFFLINE:
+#   Writes/refreshes partner confs from RAM cache → persistent location.
+#   Means if this host reboots while remote is still down, conf_cache_restore.sh
+#   can load the partner vars into RAM so fallback.sh has what it needs.
+#
+# When remote is ONLINE:
+#   Removes the persistent backup if present — not needed, conf_sync.sh will
+#   pull fresh on next boot.
+#
+# Silent when remote is online and no backup exists (normal state).
+# No-op when FALLBACK_ENABLED=false or CONF_SYNC_ENABLED=false.
+# ==============================================================================================
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "$SCRIPT_DIR/../../load_config.sh"
+
+parse_args "$@"
+detect_hosts
+
+[[ "${FALLBACK_ENABLED:-false}" != "true" ]] && exit 0
+[[ "${CONF_SYNC_ENABLED:-true}" != "true" ]] && exit 0
+[[ -z "${REMOTE_ID:-}"         ]]            && exit 0
+
+RAM_CACHE="/tmp/.cache/vv/d"
+SAVE_DIR="/boot/config/.cache/vv/d"
+
+if ping_remote; then
+    if [[ -d "$SAVE_DIR" ]]; then
+        [[ "$DRY_RUN" == true ]] && warn "DRY RUN — would remove $SAVE_DIR (remote back online)" && exit 0
+        rm -rf "$SAVE_DIR"
+        log "Remote online — persistent conf backup removed"
+    fi
+    exit 0
+fi
+
+# Remote offline — write/refresh backup from RAM cache
+if [[ ! -d "$RAM_CACHE" ]]; then
+    log "Remote offline but RAM cache not populated — nothing to back up"
+    exit 0
+fi
+
+saved=0
+for conf in "$RAM_CACHE"/host*.conf; do
+    [[ -f "$conf" ]] || continue
+    base="$(basename "$conf")"
+    [[ "${base,,}" == "${MY_ID,,}.conf" ]] && continue
+
+    if [[ "$DRY_RUN" == true ]]; then
+        warn "DRY RUN — would write $base → $SAVE_DIR/"
+        (( saved++ ))
+        continue
+    fi
+
+    mkdir -p "$SAVE_DIR"
+    cp "$conf" "$SAVE_DIR/$base" && (( saved++ ))
+done
+
+[[ "$saved" -gt 0 ]] && log "Remote offline — partner conf backup refreshed ($saved file(s))"
+exit 0