Feature/v2/pageeditor improved (#4289)

# Description of Changes

<!--
Please provide a summary of the changes, including:

Rewrite of page editor to make it work properly.  
Added page breaks
Added merged file support
Added "insert file" support
Slight Ux improvements

Closes #(issue_number)
-->

---

## 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: Anthony Stirling <[email protected]>

frontend/src/contexts/FilesModalContext.tsx

@@ -4,7 +4,7 @@ import { FileMetadata } from '../types/file';
 
 interface FilesModalContextType {
   isFilesModalOpen: boolean;
-  openFilesModal: () => void;
+  openFilesModal: (options?: { insertAfterPage?: number; customHandler?: (files: File[], insertAfterPage?: number) => void }) => void;
   closeFilesModal: () => void;
   onFileSelect: (file: File) => void;
   onFilesSelect: (files: File[]) => void;
@@ -19,30 +19,55 @@ export const FilesModalProvider: React.FC<{ children: React.ReactNode }> = ({ ch
   const { addToActiveFiles, addMultipleFiles, addStoredFiles } = useFileHandler();
   const [isFilesModalOpen, setIsFilesModalOpen] = useState(false);
   const [onModalClose, setOnModalClose] = useState<(() => void) | undefined>();
+  const [insertAfterPage, setInsertAfterPage] = useState<number | undefined>();
+  const [customHandler, setCustomHandler] = useState<((files: File[], insertAfterPage?: number) => void) | undefined>();
 
-  const openFilesModal = useCallback(() => {
+  const openFilesModal = useCallback((options?: { insertAfterPage?: number; customHandler?: (files: File[], insertAfterPage?: number) => void }) => {
+    setInsertAfterPage(options?.insertAfterPage);
+    setCustomHandler(() => options?.customHandler);
     setIsFilesModalOpen(true);
   }, []);
 
   const closeFilesModal = useCallback(() => {
     setIsFilesModalOpen(false);
+    setInsertAfterPage(undefined); // Clear insertion position
+    setCustomHandler(undefined); // Clear custom handler
     onModalClose?.();
   }, [onModalClose]);
 
   const handleFileSelect = useCallback((file: File) => {
-    addToActiveFiles(file);
+    if (customHandler) {
+      // Use custom handler for special cases (like page insertion)
+      customHandler([file], insertAfterPage);
+    } else {
+      // Use normal file handling
+      addToActiveFiles(file);
+    }
     closeFilesModal();
-  }, [addToActiveFiles, closeFilesModal]);
+  }, [addToActiveFiles, closeFilesModal, insertAfterPage, customHandler]);
 
   const handleFilesSelect = useCallback((files: File[]) => {
-    addMultipleFiles(files);
+    if (customHandler) {
+      // Use custom handler for special cases (like page insertion)
+      customHandler(files, insertAfterPage);
+    } else {
+      // Use normal file handling
+      addMultipleFiles(files);
+    }
     closeFilesModal();
-  }, [addMultipleFiles, closeFilesModal]);
+  }, [addMultipleFiles, closeFilesModal, insertAfterPage, customHandler]);
 
   const handleStoredFilesSelect = useCallback((filesWithMetadata: Array<{ file: File; originalId: string; metadata: FileMetadata }>) => {
-    addStoredFiles(filesWithMetadata);
+    if (customHandler) {
+      // Use custom handler for special cases (like page insertion)
+      const files = filesWithMetadata.map(item => item.file);
+      customHandler(files, insertAfterPage);
+    } else {
+      // Use normal file handling
+      addStoredFiles(filesWithMetadata);
+    }
     closeFilesModal();
-  }, [addStoredFiles, closeFilesModal]);
+  }, [addStoredFiles, closeFilesModal, insertAfterPage, customHandler]);
 
   const setModalCloseCallback = useCallback((callback: () => void) => {
     setOnModalClose(() => callback);