refactor: reorganize project structure into tests/, data/, logs/

- Move all backtest/simulation scripts to tests/
  - Add sys.path.insert to each script for correct import resolution
- Move pkl cache files to data/ (git-ignored)
- Move log files to logs/ (git-ignored)
- Update main.py: trading.log path → logs/trading.log
- Add ecosystem.config.js: pm2 log paths → logs/pm2*.log
- Update .gitignore: ignore data/ and logs/ instead of *.pkl/*.log
- core/fng.py: increase cache TTL 3600→86400s (API updates daily at KST 09:00)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

main.py

@@ -13,7 +13,7 @@ logging.basicConfig(
     format="%(asctime)s [%(levelname)s] %(name)s: %(message)s",
     handlers=[
         logging.StreamHandler(),
-        logging.FileHandler("trading.log", encoding="utf-8"),
+        logging.FileHandler("logs/trading.log", encoding="utf-8"),
     ],
 )