[Bug]: Merge updates already correct books

[lbird-mma]

🐛 Bug Report for Booklore

Thank you for helping us improve Booklore! Please fill out the sections below.

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📝 What happened?

When using merge in Metadata Manager, every book gets updated, also the ones that don't need an update at all. Example: I have 300+ books in 'nl' and some in 'nl-Nl', some in 'Dutch' etc. When I select all these languages, choose Merge/Split and then enter 'nl' as target language, Booklore also updates the 'nl' ones, which are already in the correct language.

I noticed this because it takes way longer for the merge to complete.

I know I can just not select the 'nl' language, but the merge shouldn't touch the already correct ones. It's just not what you expect from a Merge.

🔄 Steps to Reproduce

1. Go to Metadata Manager
2. Select Languages
3. Select multiple languages to merge

✅ Expected Behavior

Update only books with deviating metadata

📸 Screenshots / Error Messages

💻 Environment

• Version: (e.g., v1.11.0)
• OS: Ubuntu 22.04
• Browser: Opera
• Installation: Docker

📌 Additional Context

✨ Possible Solution (Optional)