Refactor mapping of text labels and bone IDs

🎯 Goal / Objective

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[!IMPORTANT]
Prerequisite issue: #352

Text annotations on an image can be clicked to navigate there. This is being handled by mapping the label text to a bone or bone part ID, in templates/js/imageAnnotationToDropdownMap.js. Preferably this would not be done in the front-end, though, so this mapping should be refactored to be stored directly in the data itself.

✅ Tasks to be Completed

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Acceptance Criteria

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• The new feature is implemented as described.
• All related code passes the repository's workflow checks (linting, tests).
• The application runs without errors after the changes are made.
• (If applicable) New automated tests have been added to cover the changes.
• Any related documentation has been updated, including JSDoc comments or docstrings

Additional Context

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First review prerequisite issue #352 and inspect templates/js/imageAnnotationToDropdownMap.js to understand how text labels map to bone or bone-part IDs. Trace where this mapping is consumed and where the related data is stored. Done means the mapping is stored in the data rather than the front end, with the application running cleanly and repository workflow checks passing.