feat: initial flight monitor

- Python flight price monitor for BER↔EZE and other routes
- Adapter pattern for extensibility (Kiwi/Tequila implemented)
- OpenClaw alerting integration
- Cron-friendly one-shot execution
- Full logging of all checks
- Graceful handling when API key not set

Implements monkey-island/flight-monitor#2

adapters/__init__.py

@@ -0,0 +1,7 @@
+"""
+Flight price adapters package.
+"""
+from adapters.base import FlightAdapter
+from adapters.kiwi import KiwiAdapter
+
+__all__ = ["FlightAdapter", "KiwiAdapter"]