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/tools/shared/NumberInputWithUnit.tsx

@@ -1,4 +1,4 @@
-import React, { useState, useEffect } from "react";
+import { useState, useEffect } from "react";
 import { Stack, Text, NumberInput } from "@mantine/core";
 
 interface NumberInputWithUnitProps {
@@ -11,14 +11,14 @@ interface NumberInputWithUnitProps {
   disabled?: boolean;
 }
 
-const NumberInputWithUnit = ({ 
-  label, 
-  value, 
-  onChange, 
-  unit, 
-  min, 
-  max, 
-  disabled = false 
+const NumberInputWithUnit = ({
+  label,
+  value,
+  onChange,
+  unit,
+  min,
+  max,
+  disabled = false
 }: NumberInputWithUnitProps) => {
   const [localValue, setLocalValue] = useState<number | string>(value);
 
@@ -54,4 +54,4 @@ const NumberInputWithUnit = ({
   );
 };
 
-export default NumberInputWithUnit;
+export default NumberInputWithUnit;