fix(plugin-cloud-storage): prevent deleting original file when duplicating

[jhb-dev]

What

Fixes the beforeChange hook in the cloud-storage-plugin to only delete files from storage when the operation is update, not during create (which includes duplication).

Why

When duplicating a media document, the originalDoc parameter is populated with the source document being duplicated. The existing condition if (originalDoc) incorrectly triggered file deletion, removing the original file from cloud storage (R2/S3/etc.) while the original database document still referenced it.

This resulted in:

• Original document in database with broken file reference
• Original file deleted from cloud storage
• New duplicated document working correctly

How

• Added operation to the destructured hook parameters
• Changed the condition from if (originalDoc) to if (originalDoc && operation === 'update')
• Files are now only deleted when genuinely updating an existing document with a new file, not when duplicating