feat: add browser implementations for advanced tools

[ConnorYoh]

14 tools now support browser-based processing (no server upload required):

Simple PDF Operations (no limitations)

1. Adjust Contrast - Image manipulation only
2. Remove Annotations - Removes form fields and annotations
3. Rotate - Rotate pages by 90/180/270 degrees
4. Remove Pages - Delete specific pages
5. Reorganize Pages - Reorder pages
6. Adjust Page Scale - Resize pages
7. Crop - Crop page dimensions
8. Single Large Page - Merge all pages vertically
9. Page Layout - Arrange pages in grid layouts

Tools with Minor Limitations

10. Flatten - Flattens forms/annotations (may not preserve all complex PDF features)
11. Change Metadata - Update PDF metadata (basic metadata only)
12. Merge - Combine PDFs (simple merge, no TOC generation or signature handling in browser)

Tools with Functional Limitations

13. Split - Split PDFs by:

• ✅ Specific pages (BY_PAGES)
• ✅ File size (BY_SIZE)
• ✅ Pages per file (BY_PAGE_COUNT)
• ✅ Number of files (BY_DOC_COUNT)
• ❌ Chapters/bookmarks (backend only)
• ❌ Page dividers (backend only)
• ❌ Sections (backend only)

14. Add Page Numbers - Add page numbers (basic text rendering, limited font support compared to backend)

Overlay Tools (complex rendering)

15. Add Stamp - Text or image stamps (font rendering limitations vs backend)
16. Add Watermark - Text or image watermarks (font rendering limitations vs backend)

Key Limitation: Browser implementations use pdf-lib which has more limited font/rendering capabilities compared to backend PDFBox. Complex PDFs with advanced features may not process perfectly in browser mode.

[stirlingbot]

🚀 Translation Verification Summary

🔄 Reference Branch: pr-branch-messages_en_GB.properties

📃 File Check: messages_en_GB.properties

1. Test Status: ✅ Passed
2. Test Status: ✅ Passed
3. Test Status: ✅ Passed

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✅ Overall Check Status: Success

Thanks @ConnorYoh for your help in keeping the translations up to date.

[stirlingbot]

✅ Frontend License Check Passed

All frontend licenses have been validated and no compatibility warnings were detected.

The frontend license report has been updated successfully.

[stirlingbot]

🚀 V2 Auto-Deployment Complete!

Your V2 PR with the new frontend/backend split architecture has been deployed!

🔗 Direct Test URL (non-SSL) http://185.252.234.121:4732

🔐 Secure HTTPS URL: https://4732.ssl.stirlingpdf.cloud

This deployment will be automatically cleaned up when the PR is closed.

🔄 Auto-deployed because PR title or branch name contains V2/version2/React keywords.