Feature/v2/file handling improvements (#4222)

# Description of Changes

A new universal file context rather than the splintered ones for the
main views, tools and manager we had before (manager still has its own
but its better integreated with the core context)
File context has been split it into a handful of different files
managing various file related issues separately to reduce the monolith -
FileReducer.ts - State management
  fileActions.ts - File operations
  fileSelectors.ts - Data access patterns
  lifecycle.ts - Resource cleanup and memory management
  fileHooks.ts - React hooks interface
  contexts.ts - Context providers
Improved thumbnail generation
Improved indexxedb handling
Stopped handling files as blobs were not necessary to improve
performance
A new library handling drag and drop
https://github.com/atlassian/pragmatic-drag-and-drop (Out of scope yes
but I broke the old one with the new filecontext and it needed doing so
it was a might as well)
A new library handling virtualisation on page editor
@tanstack/react-virtual, as above.
Quickly ripped out the last remnants of the old URL params stuff and
replaced with the beginnings of what will later become the new URL
navigation system (for now it just restores the tool name in url
behavior)
Fixed selected file not regestered when opening a tool
Fixed png thumbnails
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: Reece Browne <[email protected]>

frontend/src/hooks/usePDFProcessor.ts

@@ -1,6 +1,6 @@
 import { useState, useCallback } from 'react';
-import { getDocument } from 'pdfjs-dist';
 import { PDFDocument, PDFPage } from '../types/pageEditor';
+import { pdfWorkerManager } from '../services/pdfWorkerManager';
 
 export function usePDFProcessor() {
   const [loading, setLoading] = useState(false);
@@ -13,7 +13,7 @@ export function usePDFProcessor() {
   ): Promise<string> => {
     try {
       const arrayBuffer = await file.arrayBuffer();
-      const pdf = await getDocument({ data: arrayBuffer }).promise;
+      const pdf = await pdfWorkerManager.createDocument(arrayBuffer);
       const page = await pdf.getPage(pageNumber);
       
       const viewport = page.getViewport({ scale });
@@ -29,8 +29,8 @@ export function usePDFProcessor() {
       await page.render({ canvasContext: context, viewport }).promise;
       const thumbnail = canvas.toDataURL();
       
-      // Clean up
-      pdf.destroy();
+      // Clean up using worker manager
+      pdfWorkerManager.destroyDocument(pdf);
       
       return thumbnail;
     } catch (error) {
@@ -39,13 +39,35 @@ export function usePDFProcessor() {
     }
   }, []);
 
+  // Internal function to generate thumbnail from already-opened PDF
+  const generateThumbnailFromPDF = useCallback(async (
+    pdf: any, 
+    pageNumber: number, 
+    scale: number = 0.5
+  ): Promise<string> => {
+    const page = await pdf.getPage(pageNumber);
+    
+    const viewport = page.getViewport({ scale });
+    const canvas = document.createElement('canvas');
+    canvas.width = viewport.width;
+    canvas.height = viewport.height;
+    
+    const context = canvas.getContext('2d');
+    if (!context) {
+      throw new Error('Could not get canvas context');
+    }
+    
+    await page.render({ canvasContext: context, viewport }).promise;
+    return canvas.toDataURL();
+  }, []);
+
   const processPDFFile = useCallback(async (file: File): Promise<PDFDocument> => {
     setLoading(true);
     setError(null);
     
     try {
       const arrayBuffer = await file.arrayBuffer();
-      const pdf = await getDocument({ data: arrayBuffer }).promise;
+      const pdf = await pdfWorkerManager.createDocument(arrayBuffer);
       const totalPages = pdf.numPages;
       
       const pages: PDFPage[] = [];
@@ -61,19 +83,19 @@ export function usePDFProcessor() {
         });
       }
       
-      // Generate thumbnails for first 10 pages immediately for better UX
+      // Generate thumbnails for first 10 pages immediately using the same PDF instance
       const priorityPages = Math.min(10, totalPages);
       for (let i = 1; i <= priorityPages; i++) {
         try {
-          const thumbnail = await generatePageThumbnail(file, i);
+          const thumbnail = await generateThumbnailFromPDF(pdf, i);
           pages[i - 1].thumbnail = thumbnail;
         } catch (error) {
           console.warn(`Failed to generate thumbnail for page ${i}:`, error);
         }
       }
       
-      // Clean up
-      pdf.destroy();
+      // Clean up using worker manager
+      pdfWorkerManager.destroyDocument(pdf);
       
       const document: PDFDocument = {
         id: `${Date.now()}-${Math.random().toString(36).substr(2, 9)}`,
@@ -91,7 +113,7 @@ export function usePDFProcessor() {
     } finally {
       setLoading(false);
     }
-  }, [generatePageThumbnail]);
+  }, [generateThumbnailFromPDF]);
 
   return {
     processPDFFile,