fix: Correct detection box rendering with letterboxed/pillarboxed video

[ebowwa]

Summary

Fixes detection boxes appearing as vertical lines when video is letterboxed or pillarboxed.

Problem

Detection coordinates are normalized to original video dimensions, but were being transformed using the container geometry size. This caused incorrect rendering when the video aspect ratio differed from the container.

Solution

Modified prepareObjectForSwiftUI to accept an optional videoSize parameter:

• Uses actual video dimensions for coordinate transformation
• Scales transformed coordinates to fit the container geometry
• Maintains backward compatibility

Test Plan

• ✅ Build succeeds
• ✅ App launches correctly
• ✅ Detection boxes now render with proper aspect ratios

Related

Fixes: andrewginns#3
Upstream PR: andrewginns#4

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