add opencv-python to requirements.txt (#2061)

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## Summary by CodeRabbit

* **Chores**
* Updated project install-time dependencies to include OpenCV
(opencv-python), ensuring the runtime now bundles OpenCV’s Python
bindings.
* Dependency-only change; no public interfaces or exported entities were
modified.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Signed-off-by: guozijn <guozijn@gmail.com>