🔄 refactor: Migrate to react-resizable-panels v4 with Artifacts Header polish (#12356)

* chore: Update react-resizable-panels dependency to version 4.7.4

- Upgraded the "react-resizable-panels" package in package-lock.json, package.json, and client package.json files to ensure compatibility with the latest features and improvements.
- Adjusted peer dependencies for React and ReactDOM to align with the new version requirements.

* refactor: Update Share and SidePanel components to `react-resizable-panels` v4

- Refactored the ShareArtifactsContainer to utilize a new layout change handler, enhancing artifact panel resizing functionality.
- Updated ArtifactsPanel to use the new `usePanelRef` hook, improving panel reference management.
- Simplified SidePanelGroup by removing unnecessary layout normalization and integrating default layout handling with localStorage.
- Removed the deprecated `normalizeLayout` utility function to streamline the codebase.
- Adjusted Resizable components to ensure consistent sizing and layout behavior across panels.

* style: Enhance scrollbar appearance across application

- Added custom scrollbar styles to both artifacts and markdown files, improving aesthetics and user experience.
- Implemented dark mode adjustments for scrollbar visibility, ensuring consistency across different color schemes.

* style: Standardize button sizes and layout in Artifacts components

- Updated button dimensions to a consistent height of 9 units across various components including Artifacts, Code, and DownloadArtifact.
- Adjusted padding and layout properties in the Artifacts header for improved visual consistency.
- Enhanced the Radio component to accept a new `buttonClassName` prop for better customization of button styles.

* chore: import order

client/package.json

@@ -95,7 +95,7 @@
     "react-hook-form": "^7.43.9",
     "react-i18next": "^15.4.0",
     "react-markdown": "^9.0.1",
-    "react-resizable-panels": "^3.0.6",
+    "react-resizable-panels": "^4.7.4",
     "react-router-dom": "^6.30.3",
     "react-speech-recognition": "^3.10.0",
     "react-textarea-autosize": "^8.4.0",