refactor(frontend): remove unused React default imports (#4529)

## Description of Changes

- Removed unused `React` default imports across multiple frontend
components.
- Updated imports to only include required React hooks and types (e.g.,
`useState`, `useEffect`, `Suspense`, `createContext`).
- Ensured consistency with React 17+ JSX transform, where default
`React` import is no longer required.
- This cleanup reduces bundle size slightly and aligns code with modern
React best practices.

---

## Checklist

### General

- [ ] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] 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)
- [ ] I have performed a self-review of my own code
- [ ] 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)

### 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)

- [ ] 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.

Co-authored-by: Reece Browne <74901996+reecebrowne@users.noreply.github.com>

frontend/src/components/toast/ToastRenderer.tsx

@@ -1,4 +1,3 @@
-import React from 'react';
 import { useToast } from './ToastContext';
 import { ToastInstance, ToastLocation } from './types';
 import { LocalIcon } from '../shared/LocalIcon';
@@ -66,7 +65,7 @@ export default function ToastRenderer() {
                       <LocalIcon icon={`material-symbols:${getDefaultIconName(t)}`} width={20} height={20} />
                     )}
                   </div>
-                  
+
                   {/* Title + count badge */}
                   <div className="toast-title-container">
                     <span>{t.title}</span>
@@ -74,7 +73,7 @@ export default function ToastRenderer() {
                       <span className="toast-count-badge">{t.count}</span>
                     )}
                   </div>
-                  
+
                   {/* Controls */}
                   <div className="toast-controls">
                     {t.expandable && (
@@ -101,20 +100,20 @@ export default function ToastRenderer() {
                 {/* Progress bar - always show when present */}
                 {typeof t.progress === 'number' && (
                   <div className="toast-progress-container">
-                    <div 
+                    <div
                       className={getProgressBarClass(t)}
                       style={{ width: `${t.progress}%` }}
                     />
                   </div>
                 )}
-                
+
                 {/* Body content - only show when expanded */}
                 {(t.isExpanded || !t.expandable) && (
                   <div className="toast-body">
                     {t.body}
                   </div>
                 )}
-                
+
                 {/* Button - always show when present, positioned below body */}
                 {t.buttonText && t.buttonCallback && (
                   <div className="toast-action-container">