fix(ui): increased button clickability and shifted them downward

[LJX2017]

What changes were proposed in this PR?

This PR fixes the clickability issue of the "Add port" (+) and "Remove port" (-) buttons.

1. Added transparent clickable rectangle overlay to port buttons: Added a element with fill="transparent" and pointer-events="all" to each port button SVG (add/remove input/output port buttons). This creates an invisible clickable area that matches the shape of the button's circle outline, making the entire button area clickable instead of just the thin "+", "o", or "-" symbols.

Any related issues, documentation, discussions?

Fixes #4028

How was this PR tested?

Manually tested.

2025-11-11.03-03-40.mp4

Was this PR authored or co-authored using generative AI tooling?

No

[chenlica]

@mengw15 Can you review it? After that, @aicam can review it.

[mengw15]

LGTM