chore: remove unused [video] OpenCV optional dependency

[TrueFurina]

Summary

Removes the unused [video] optional dependency (opencv-python) from pyproject.toml. The codebase does not use OpenCV or provide video metadata functionality, so this extra made the package surface larger than necessary and implied a capability that does not exist.

Changes

• pyproject.toml: removed video = ["opencv-python>=4.9,<5"] from [project.optional-dependencies]

Acceptance criteria

• video optional dependency removed from pyproject.toml
• No OpenCV dependency remains in project metadata
• Existing image/HEIF metadata behavior unchanged (Pillow + pillow-heif untouched)
• Existing tests/lint unaffected (no test references the video extra)

[quangshuynh]

Thanks for the contribution! This keeps the package metadata aligned with the functionality the project actually supports and stays nicely scoped to the issue

CI is green and the existing image/HEIF dependencies are unchanged, so this looks good to merge