[UI] Add an auto-scroll feature to connect edges on huge scenes

[Alxiice]

Description

When scenes are too big and we want to connect nodes that cannot be seen at the same time, it's not convenient to create edges.

This PR aims to add an "auto-scroll" feature that will move the graph when we approach the edges of the graph editor. This way users can easily drag edges, move in the graph and connect the edges.

Notes for the review

Aside from the code review I would like to know what would be the best settings for

• the border margins (threshold where the scroll is enabled)
• the scroll speed

Demo

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.75%. Comparing base (507e2dc) to head (567d3d9).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #3159   +/-   ##
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  Coverage    85.75%   85.75%           
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  Files           78       78           
  Lines        12087    12087           
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  Hits         10365    10365           
  Misses        1722     1722           

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[gemini-code-assist]

Code Review

This pull request introduces an autoscroll feature to the Graph Editor when dragging attribute pin edges near the workspace boundaries. It also refactors the QmlInstantEngine to inherit from QObject instead of QQmlApplicationEngine to facilitate cleaner hot-reloads. The review feedback identifies several key issues: inefficient signal emission and a correctness bug in the edge dragging logic of AttributePin.qml, potential runaway scrolling speeds when dragging far outside the Graph Editor boundaries, and a missing parent reference for a QTimer in utils.py that could lead to memory leaks.

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