Refine cropping between markers and detect flow display for OCR

[GrilledYo]

Summary

• crop the marker-delimited region using contour bounds so the result stays inside the red circles
• automatically locate the dark flow display within the cropped image and fall back to the legacy crop if needed
• propagate the new origin offsets when saving OCR results and warn when the fallback logic triggers

Testing

• python -m compileall process_image.py

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https://chatgpt.com/codex/tasks/task_b_68faade366088330a78c3150b00191bc