Add runbook for recovering wedged units and new scripts for device management

- Created a comprehensive runbook (`wedged_unit_recovery.md`) detailing the recovery process for units stuck in a call-home loop, including symptoms, recovery steps, and explanations of the failure mode.
- Added `blind_stop.sh` script to send stop-monitoring commands in a tight loop for unresponsive devices.
- Introduced `rescue_device.sh` script to disable Auto Call Home and erase events from a busy device.
- Implemented `slow_drip.sh` script to send stop-monitoring frames at a slow rate to prevent UART overrun.
- Developed `spam_stop.sh` script to rapidly send stop-monitoring commands to a device.
- Created `watch_unit.sh` script for passive monitoring of device reachability, logging results over time.

scripts/slow_drip.sh

@@ -0,0 +1,44 @@
+#!/usr/bin/env bash
+# Hold a single TCP session open and drip stop-monitoring frames at a slow
+# rate, so the device's UART RX FIFO has time to drain between sends.
+#
+# Use when high-rate spam isn't landing — typically because the device's
+# firmware is too busy to drain its serial buffer fast enough and bytes
+# are being lost to UART overrun.
+#
+# Usage:
+#   ./slow_drip.sh <host> [tcp_port] [duration_s]
+#
+# Env:
+#   DURATION         Default: 120 (seconds; arg 3 overrides). Clamped 1..600.
+#   INTERVAL         Seconds between drip sends (default 3).  Lower = more
+#                    aggressive, more risk of FIFO overrun.  Higher = safer
+#                    but fewer total drips per duration.
+#   CONNECT_TIMEOUT  Default: 5
+#   SFM_BASE_URL     Default: http://localhost:8200 (SFM direct).
+
+set -u
+
+host="${1:-}"
+tcp_port="${2:-9034}"
+duration="${3:-${DURATION:-120}}"
+if [[ -z "$host" ]]; then
+  echo "usage: $0 <host> [tcp_port] [duration_s]" >&2
+  exit 2
+fi
+
+base="${SFM_BASE_URL:-http://localhost:8200}"
+interval="${INTERVAL:-3}"
+connect_timeout="${CONNECT_TIMEOUT:-5}"
+
+url="${base}/device/stop_monitoring_slow_drip?host=${host}&tcp_port=${tcp_port}&duration_s=${duration}&interval_s=${interval}&connect_timeout=${connect_timeout}"
+
+echo "slow_drip: target ${host}:${tcp_port}  duration=${duration}s  interval=${interval}s  connect_timeout=${connect_timeout}s"
+echo "slow_drip: POST ${url}"
+echo
+
+# Give curl enough slack to wait out the duration plus a buffer
+max_time=$(awk -v d="$duration" 'BEGIN { printf "%d", d + 30 }')
+
+curl -sS --max-time "$max_time" -X POST "$url"
+echo