feat: Enable logging to file for persistent MEV bot logs

- Configure log output to logs/mev-bot.log instead of stdout only
- Create logs directory structure for organized log management
- Enable persistent logging for long-running MEV monitoring sessions

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

config/config.yaml

@@ -73,7 +73,7 @@ log:
   # Log format (json, text)
   format: "text"
   # Log file path (empty for stdout)
-  file: ""
+  file: "logs/mev-bot.log"
 
 # Database configuration
 database: