[Feature] Sign PDF (E-Sign)

[ayushcmd]

Summary

Draw, type, or upload a signature and embed it into PDF.

Files to create/edit

• src/pages/tools/SignPdf.tsx → create
• src/App.tsx → add import + route /tools/sign-pdf
• src/pages/Tools.tsx → add to allTools[]
• src/components/home/ToolsGrid.tsx → add card

Implementation notes

• Canvas-based signature drawing via react-signature-canvas
• Type mode: render text as signature font
• Upload mode: accept PNG signature image
• Place signature on page via drag, export with pdf-lib

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