Pan not working over selecting imports

[MarkJB]

This pull request improves mouse interaction handling on the canvas by making right-click (mouse button 2) consistently initiate panning, in addition to the existing middle-click (button 1) support. It also ensures that only primary mouse button interactions trigger object manipulation (drag, scale, rotate, group bounding box handles), preventing accidental gestures with right or middle clicks. The tests are updated to cover these behaviors.

Mouse interaction and event handling improvements:

• Updated useCanvasInteractionHandlers to allow both right-click (button 2) and middle-click (button 1) to start panning the canvas, and to prevent default browser behavior for these buttons.
• Added a shared isNonPrimaryButton utility in several hooks (useObjectDrag, useObjectScaleRotate, useGroupOBB) to ensure that only primary button (button 0, usually left-click) can trigger object drag, scale, rotate, or group bounding box handle actions. [1] [2] [3] [4] [5] [6] [7]

Testing enhancements:

• Added and improved tests in PlotCanvas.test.tsx to verify that right-click can pan the canvas, and that right-clicking on an import pans the canvas without moving the import itself. Also, refactored the ResizeObserver setup utility for reuse and removed duplicate code. [1] [2] [3]

[MarkJB]

Relates to issue #36