fix(ui): popup list controls overlap with table in list view (#13967)

### What?
- Fixes an issue where the table header row was overlapping menu items
in the ListControls component.

### Why?
- The overlapping occurred because the table lacked proper stacking
context, causing z-index rules to affecting the visibility and usability
of menu items in the ListControls component rendered above the table.

### How?
- Added the CSS property isolation: isolate to the table styles. This
creates a new stacking context, ensuring that the table header does not
interfere with overlapping UI elements

### UI Changes:
Before:
<img width="1357" height="730" alt="image"
src="https://github.com/user-attachments/assets/703f7bbe-0cd7-4dfb-a584-a6436a0ea5d7"
/>

After:
<img width="1357" height="730" alt="image"
src="https://github.com/user-attachments/assets/927c904a-4423-420b-ad4d-0a3c4624b5ee"
/>

Fixes #13941 

<!--

Thank you for the PR! Please go through the checklist below and make
sure you've completed all the steps.

Please review the
[CONTRIBUTING.md](https://github.com/payloadcms/payload/blob/main/CONTRIBUTING.md)
document in this repository if you haven't already.

The following items will ensure that your PR is handled as smoothly as
possible:

- PR Title must follow conventional commits format. For example, `feat:
my new feature`, `fix(plugin-seo): my fix`.
- Minimal description explained as if explained to someone not
immediately familiar with the code.
- Provide before/after screenshots or code diffs if applicable.
- Link any related issues/discussions from GitHub or Discord.
- Add review comments if necessary to explain to the reviewer the logic
behind a change

### What?

### Why?

### How?

Fixes #

-->