feat: Minimize site form layout shift

[dcalhoun]

Proposed Changes

Minimize site form layout shift
The "Add site" dialog relies upon asynchronous name generation, which
ultimately populates the site path input. Conditionally rendering the
site path input based upon the populated site path value meant the input
popped into place during the modal open animation. Conditionally
rendering the input based upon the event handler only ensures the input
is present throughout the modal open animation.

Testing Instructions

Tip

Observing the difference in the provided screen recordings below requires slowly dragging the video scrubber.

Before	After
initial-open-before.mov	initial-open-after.mov
	repeat-open-after.mov

1. Add site dialog always displays site path input

1. Click "Add site" in the sidebar.
2. Verify the site path input is always in-place, even during the modal
   animation the first time the modal is opened.

2. Edit site name excludes site path input

1. Select or add a site.
2. Navigate to the Settings panel.
3. Click "Edit" next to the site name.
4. Verify the site path input is not displayed.

Pre-merge Checklist

• Have you checked for TypeScript, React or other console errors?

[dcalhoun]

I consider the proposed changes an easy, low-quality solution, but I feel they are sufficient for the time being.

A more ideal solution might involve rendering a placeholder until the asynchronous work is complete. We might also postpone rendering of the actual dialog content until after both the modal open animation and asynchronous name generation complete to achieve optimal FPS.

[katinthehatsite]

The changes look good and fix the issue for me. Thanks for adding the fix!