Fix low recall when limit_val_batches is set

[vickysharma-prog]

Description

When limit_val_batches is set (e.g., 0.1 for 10%), evaluation loads the full ground truth CSV but predictions only cover the limited images. This makes recall look very low because of "missing" predictions for images that were never processed.

Added a check in __evaluate__ that trims ground_df based on limit_val_batches value. Uses ceil(limit_val_batches * n_images) as suggested in the issue.

Also added a test case to verify the fix.

Related Issue(s)

Fixes #1232

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