fix(automation): add zIndex and withinPortal props to dropdown components for improved UI consistency (#5527)

# Description of Changes
Closes: #5525
Closes: #5242


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- Why the change was made
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## Checklist

### General

- [X] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [X] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [X] I have performed a self-review of my own code
- [X] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### Translations (if applicable)

- [ ] I ran
[`scripts/counter_translation.py`](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/docs/counter_translation.md)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [X] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md#6-testing)
for more details.

Signed-off-by: Balázs Szücs <[email protected]>

frontend/src/core/components/tools/overlayPdfs/OverlayPdfsSettings.tsx

@@ -4,6 +4,7 @@ import { type OverlayPdfsParameters, type OverlayMode } from '@app/hooks/tools/o
 import LocalIcon from '@app/components/shared/LocalIcon';
 import { useFilesModalContext } from '@app/contexts/FilesModalContext';
 import styles from '@app/components/tools/overlayPdfs/OverlayPdfsSettings.module.css';
+import { Z_INDEX_AUTOMATE_DROPDOWN } from "@app/styles/zIndex";
 
 interface OverlayPdfsSettingsProps {
   parameters: OverlayPdfsParameters;
@@ -56,6 +57,7 @@ export default function OverlayPdfsSettings({ parameters, onParameterChange, dis
           value={parameters.overlayMode}
           onChange={(v) => handleModeChange((v || 'SequentialOverlay') as OverlayMode)}
           disabled={disabled}
+          comboboxProps={{ withinPortal: true, zIndex: Z_INDEX_AUTOMATE_DROPDOWN }}
         />
       </Stack>