fix: reject degenerate polygons in AOI area validation

[heathdutton]

Fixes #228

When drawing an AOI at low zoom levels, the polygon coordinates can collapse to nearly identical points, resulting in a degenerate polygon with zero area. The validateGeoJSONArea function was incorrectly returning false (valid) for these cases instead of true (invalid). Confused? So was I.

This one-line fix correctly rejects polygons with zero, NaN, or invalid area values.

[kshitijrajsharma]

Thanks @heathdutton for the PR , we will be reviewing this soon !

[jeafreezy]

Thank you for your contribution @heathdutton .

The issue this PR intends to fix was happening before the latest development on fAIr. As of now, you can't experience the bug again because we now have a minimum size for drawing a polygon. See attached video for context.

Screen.Recording.2026-01-18.at.17.22.34.mov

Nevertheless, we'll have this PR opened for merging should such issue come up again in the future.

Thank you!

[jeafreezy]

See #465 (comment)

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