fix: implement proper PATCH behavior for report updates

[Kanishkavijay39]

• Fix patchReport to merge existing data with patch data instead of replacing entirely
• Add getS3Object function to fetch existing report data from S3
• Implement shallow merge where patch data takes precedence over existing data
• Update tests to reflect proper PATCH merge behavior
• Add comprehensive test cases for merge functionality and error handling

Fixes issue where PATCH requests were losing existing report fields that weren't included in the patch payload.

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Related Issues

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This PR will trigger a patch release when merged.