V2 flatten (#4358)

# Description of Changes

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Please provide a summary of the changes, including:

- What was changed
- Why the change was made
- Any challenges encountered

Closes #(issue_number)
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---

## 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: James Brunton <[email protected]>
Co-authored-by: ConnorYoh <[email protected]>

frontend/src/hooks/tools/flatten/useFlattenOperation.ts

@@ -0,0 +1,33 @@
+import { useTranslation } from 'react-i18next';
+import { ToolType, useToolOperation } from '../shared/useToolOperation';
+import { createStandardErrorHandler } from '../../../utils/toolErrorHandler';
+import { FlattenParameters, defaultParameters } from './useFlattenParameters';
+
+// Static function that can be used by both the hook and automation executor
+export const buildFlattenFormData = (parameters: FlattenParameters, file: File): FormData => {
+  const formData = new FormData();
+  formData.append('fileInput', file);
+  formData.append('flattenOnlyForms', parameters.flattenOnlyForms.toString());
+  return formData;
+};
+
+// Static configuration object
+export const flattenOperationConfig = {
+  toolType: ToolType.singleFile,
+  buildFormData: buildFlattenFormData,
+  operationType: 'flatten',
+  endpoint: '/api/v1/misc/flatten',
+  filePrefix: 'flattened_', // Will be overridden in hook with translation
+  multiFileEndpoint: false,
+  defaultParameters,
+} as const;
+
+export const useFlattenOperation = () => {
+  const { t } = useTranslation();
+
+  return useToolOperation<FlattenParameters>({
+    ...flattenOperationConfig,
+    filePrefix: t('flatten.filenamePrefix', 'flattened') + '_',
+    getErrorMessage: createStandardErrorHandler(t('flatten.error.failed', 'An error occurred while flattening the PDF.'))
+  });
+};

frontend/src/hooks/tools/flatten/useFlattenParameters.ts

@@ -0,0 +1,19 @@
+import { BaseParameters } from '../../../types/parameters';
+import { useBaseParameters, BaseParametersHook } from '../shared/useBaseParameters';
+
+export interface FlattenParameters extends BaseParameters {
+  flattenOnlyForms: boolean;
+}
+
+export const defaultParameters: FlattenParameters = {
+  flattenOnlyForms: false,
+};
+
+export type FlattenParametersHook = BaseParametersHook<FlattenParameters>;
+
+export const useFlattenParameters = (): FlattenParametersHook => {
+  return useBaseParameters({
+    defaultParameters,
+    endpointName: 'flatten',
+  });
+};