feat: flight price monitor with Kiwi adapter stub and cron setup

- config.json: BER→EZE route, €700 threshold, 14-28 nights, Dec-Mar preferred
- monitor.py: config-driven, multi-route, windowed date search, openclaw alerts
- adapters/base.py: abstract FlightAdapter interface
- adapters/kiwi.py: Kiwi/Tequila v2 adapter (stub until KIWI_API_KEY is set)
- requirements.txt, cron-install.sh (daily 08:00 UTC), README.md

cron-install.sh

@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+# Install a daily cron job to run the flight monitor at 08:00 UTC.
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PYTHON="$(command -v python3 || command -v python)"
+CRON_CMD="0 8 * * * $PYTHON $SCRIPT_DIR/monitor.py >> $SCRIPT_DIR/monitor.log 2>&1"
+MARKER="flight-monitor"
+
+# Check if already installed
+if crontab -l 2>/dev/null | grep -q "$MARKER"; then
+    echo "✅ Cron job already installed (contains '$MARKER'). Nothing changed."
+    exit 0
+fi
+
+# Append new entry (preserve existing crontab)
+(crontab -l 2>/dev/null || true; echo "# $MARKER"; echo "$CRON_CMD") | crontab -
+
+echo "✅ Cron job installed:"
+echo "   $CRON_CMD"
+echo ""
+echo "Runs daily at 08:00 UTC. Logs → $SCRIPT_DIR/monitor.log"