Offline pdfium (#5213)

# 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.

frontend/vite.config.ts

@@ -1,6 +1,7 @@
 import { defineConfig } from 'vite';
 import react from '@vitejs/plugin-react-swc';
 import tsconfigPaths from 'vite-tsconfig-paths';
+import { viteStaticCopy } from 'vite-plugin-static-copy';
 
 export default defineConfig(({ mode }) => {
   // When DISABLE_ADDITIONAL_FEATURES is false (or unset), enable proprietary features
@@ -20,6 +21,15 @@ export default defineConfig(({ mode }) => {
       tsconfigPaths({
         projects: [tsconfigProject],
       }),
+      viteStaticCopy({
+        targets: [
+          {
+            //provides static pdfium so embedpdf can run without cdn
+            src: 'node_modules/@embedpdf/pdfium/dist/pdfium.wasm',
+            dest: 'pdfium'
+          }
+        ]
+      })
     ],
     server: {
       host: true,