Multi annotation

[inesdv26]

This pull request introduces a dropdown menu that allows users to toggle between two modes:
Single Annotation Mode: in this mode, the color of the bounding boxes remains fixed and cannot be changed.
Multi-Annotation Mode: users can change the color of the bounding boxes using the following keyboard shortcuts:

• Press 'G' to change the box color to green.
• Press 'H' to change the box color to blue.
• Press 'Z' to reset the bounding box to its original color.
  When the 'Save Boxes' button is clicked, the class label of the organoid is determined based on the bounding box color:
• Class Label 0 for green.
• Class Label 1 for blue.

[francesco-campi]

Good job, the tool has all the features we discussed about. I left you a few comments to improve the code structure and the way you display messages. Let me know what do you think.

[francesco-campi]

NIce, it looks good! I left you two minor comments, after this we can merge into the main brach.