Add hotkey to assign empty label

[jpggvilaca]

📝 Description

• Pressing "n" should now assign "Empty" label for Detection project and "No object" for segmentation projects

✨ Type of Change

Select the type of change your PR introduces:

• 🐞 Bug fix – Non-breaking change which fixes an issue
• 🚀 New feature – Non-breaking change which adds functionality
• 🔨 Refactor – Non-breaking change which refactors the code base
• 💥 Breaking change – Changes that break existing functionality
• 📚 Documentation update
• 🔒 Security update
• 🧪 Tests

🧪 Testing Scenarios

Describe how the changes were tested and how reviewers can test them too:

• ✅ Tested manually
• 🤖 Run automated end-to-end tests

✅ Checklist

Before submitting the PR, ensure the following:

• 🔍 PR title is clear and meaningful
• ✍️ PR description clearly explains the changes and their reason
• 📝 I have linked the PR to the corresponding GitHub Issues, if any
• 💬 I have commented my code, especially in hard-to-understand areas
• 📄 I have made corresponding changes to the documentation
• ✅ I have added tests that prove my fix is effective or my feature works

[Copilot]

Pull Request Overview

This PR adds a new hotkey ('n') to assign an empty label to selected annotations in the annotator interface. This feature enables users to quickly assign empty labels without manually clicking through the UI.

Key changes:

• Added 'empty-label' hotkey action type and default key binding ('n')
• Implemented hotkey handler that assigns empty label to selected annotations when triggered

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
web_ui/src/pages/annotator/providers/annotator-provider/utils.ts	Added 'empty-label' to HotKeyActions type and DefaultHotkeys configuration with 'n' key binding
web_ui/src/pages/annotator/components/primary-toolbar/hot-keys-button/use-availability-of-hotkeys.hook.ts	Enabled the 'empty-label' hotkey by setting its availability to true
web_ui/src/pages/annotator/components/main-content/labels-shortcuts/labels-shortcuts.component.tsx	Implemented the hotkey handler that finds the empty label and assigns it to selected annotations

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

[MarkRedeman]

Why is the check being made on the selected annotations? For detection and segmentation the empty label can also be when the user has no annotations selected - for local annotation projects we always replace the whole scene with a single "full image" annotation that only has the empty label.

[jpggvilaca]

True! I wasnt 100% sure. Updated :)