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

.gitignore

@@ -0,0 +1,14 @@
+__pycache__/
+*.pyc
+*.pyo
+*.pyd
+.Python
+*.so
+*.egg
+*.egg-info/
+dist/
+build/
+.env
+.venv
+venv/
+monitor.log