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>

.gitignore

@@ -2,5 +2,5 @@
 __pycache__/
 *.pyc
 .venv/
-*.log
-*.pkl
+logs/
+data/