Stirling 2.0 (#3928)

# Description of Changes

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File context for managing files between tools and views
Optimisation for large files
Updated Split to work with new file system and match Matts stepped
design closer

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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: Anthony Stirling <[email protected]>

frontend/src/hooks/usePDFProcessor.ts

@@ -50,18 +50,28 @@ export function usePDFProcessor() {
       
       const pages: PDFPage[] = [];
       
-      // Generate thumbnails for all pages
+      // Create pages without thumbnails initially - load them lazily
       for (let i = 1; i <= totalPages; i++) {
-        const thumbnail = await generatePageThumbnail(file, i);
         pages.push({
           id: `${file.name}-page-${i}`,
           pageNumber: i,
-          thumbnail,
+          thumbnail: null, // Will be loaded lazily
           rotation: 0,
           selected: false
         });
       }
       
+      // Generate thumbnails for first 10 pages immediately for better UX
+      const priorityPages = Math.min(10, totalPages);
+      for (let i = 1; i <= priorityPages; i++) {
+        try {
+          const thumbnail = await generatePageThumbnail(file, i);
+          pages[i - 1].thumbnail = thumbnail;
+        } catch (error) {
+          console.warn(`Failed to generate thumbnail for page ${i}:`, error);
+        }
+      }
+      
       // Clean up
       pdf.destroy();