V2 flatten (#4358)

# Description of Changes

<!--
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 <jbrunton96@gmail.com>
Co-authored-by: ConnorYoh <40631091+ConnorYoh@users.noreply.github.com>

frontend/src/tools/Flatten.tsx

@@ -0,0 +1,62 @@
+import { useTranslation } from "react-i18next";
+import { createToolFlow } from "../components/tools/shared/createToolFlow";
+import FlattenSettings from "../components/tools/flatten/FlattenSettings";
+import { useFlattenParameters } from "../hooks/tools/flatten/useFlattenParameters";
+import { useFlattenOperation } from "../hooks/tools/flatten/useFlattenOperation";
+import { useBaseTool } from "../hooks/tools/shared/useBaseTool";
+import { useFlattenTips } from "../components/tooltips/useFlattenTips";
+import { BaseToolProps, ToolComponent } from "../types/tool";
+
+const Flatten = (props: BaseToolProps) => {
+  const { t } = useTranslation();
+  const flattenTips = useFlattenTips();
+
+  const base = useBaseTool(
+    'flatten',
+    useFlattenParameters,
+    useFlattenOperation,
+    props
+  );
+
+  return createToolFlow({
+    files: {
+      selectedFiles: base.selectedFiles,
+      isCollapsed: base.hasResults,
+      placeholder: t("flatten.files.placeholder", "Select a PDF file in the main view to get started"),
+    },
+    steps: [
+      {
+        title: t("flatten.options.stepTitle", "Flatten Options"),
+        isCollapsed: base.settingsCollapsed,
+        onCollapsedClick: base.settingsCollapsed ? base.handleSettingsReset : undefined,
+        tooltip: flattenTips,
+        content: (
+          <FlattenSettings
+            parameters={base.params.parameters}
+            onParameterChange={base.params.updateParameter}
+            disabled={base.endpointLoading}
+          />
+        ),
+      },
+    ],
+    executeButton: {
+      text: t("flatten.submit", "Flatten PDF"),
+      isVisible: !base.hasResults,
+      loadingText: t("loading"),
+      onClick: base.handleExecute,
+      disabled: !base.params.validateParameters() || !base.hasFiles || !base.endpointEnabled,
+    },
+    review: {
+      isVisible: base.hasResults,
+      operation: base.operation,
+      title: t("flatten.results.title", "Flatten Results"),
+      onFileClick: base.handleThumbnailClick,
+      onUndo: base.handleUndo,
+    },
+  });
+};
+
+// Static method to get the operation hook for automation
+Flatten.tool = () => useFlattenOperation;
+
+export default Flatten as ToolComponent;