GRAPH DIRECTION UPLOAD (v14)

Bugfix:
- The chart can occupy most of the image bbox after bridging, so the old code mistakenly rejected it.
- Now we only reject huge components if they are DENSE (filled UI blocks), not line-like charts.

Run:
  python -m venv .venv
  .\.venv\Scripts\Activate.ps1
  pip install -r requirements.txt
  python app.py

Open:
  http://127.0.0.1:5000
