CBG-5134: attachment fetch is in wrong place when loading from bucket by CV

[gregns1]

CBG-5134

• Was always fetch current revision attachments when loading from bucket. This is not correct when dealing with backup revision.

Pre-review checklist

• Removed debug logging (fmt.Print, log.Print, ...)
• Logging sensitive data? Make sure it's tagged (e.g. base.UD(docID), base.MD(dbName))
• Updated relevant information in the API specifications (such as endpoint descriptions, schemas, ...) in docs/api

Dependencies (if applicable)

• Link upstream PRs
• Update Go module dependencies when merged

Integration Tests

• GSI=true,xattrs=true https://jenkins.sgwdev.com/job/SyncGatewayIntegration/244/

[Copilot]

Pull request overview

This PR fixes a bug where attachment fetching was incorrectly occurring when loading backup revisions from the bucket. The fix ensures that attachments are only fetched for the current revision, not for backup revisions accessed by their current version (CV).

Changes:

• Moved attachment fetching logic inside the conditional block that handles current revision loading
• Added test coverage to verify that fetching a backup revision (when the current revision has attachments) correctly returns an empty attachments map

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
db/revision_cache_interface.go	Moved attachments = doc.Attachments() inside the conditional block to prevent fetching attachments for backup revisions
db/attachment_test.go	Added test to verify backup revision retrieval doesn't incorrectly fetch current revision attachments

Comments suppressed due to low confidence (1)

db/attachment_test.go:11

• The fmt import is used only for fmt.Sprintf in test setup code. This is acceptable for tests, but verify that no debug logging with fmt.Print* functions remains in the codebase.

import (