[Feature] Redact PDF

[ayushcmd]

Summary

Permanently black out selected text or regions in PDF.

Files to create/edit

• src/pages/tools/RedactPdf.tsx → create
• src/App.tsx → add import + route /tools/redact-pdf
• src/pages/Tools.tsx → add to allTools[]

Implementation notes

• Render PDF via pdfjs-dist canvas
• Let user draw rectangles over regions to redact
• Use pdf-lib to draw filled black rectangles permanently