Add copy button for TD affordances (actions, properties, events)

[AyushPrakash414]

Fixes #57

This PR adds a copy button for Thing Description affordances (actions, properties, and events) in the visual editor.

Users can now duplicate similar affordances directly from the UI without switching to the JSON editor, improving usability and workflow efficiency.

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[egekorkan]

• handleCopyXXX functions can be refactored to not copy paste the same thing
• You need to sign your commits and link your Eclipse account. Make sure to read https://github.com/eclipse/editdor/blob/master/CONTRIBUTING.md
• It would be muuuch better if the new affordance is just under the copied affordance. With longer TDs, it is very difficult to find it. Also, there is no visual confirmation that a new affordance is added.

[AyushPrakash414]

• handleCopyXXX functions can be refactored to not copy paste the same thing
• You need to sign your commits and link your Eclipse account. Make sure to read https://github.com/eclipse/editdor/blob/master/CONTRIBUTING.md
• It would be muuuch better if the new affordance is just under the copied affordance. With longer TDs, it is very difficult to find it. Also, there is no visual confirmation that a new affordance is added.

Changes include:

• Refactored affordance copy logic into a shared helper
• Insert copied affordance directly below the original
• Added visual confirmation via auto-expand and scroll

All commits are signed and Eclipse Contributor Agreement requirements are fulfilled.