Add PDF export feature to notes

- Installed jsPDF and html2canvas libraries
- Implemented handleExportPDF function to convert note to PDF
- Creates temporary styled container with title and content
- Uses html2canvas to render content as image
- Generates A4 format PDF with proper formatting
- Added export button (download icon) in note header
- Button positioned between discard and favorite buttons
- PDF filename uses note title
- Includes error handling with user feedback

package.json

@@ -17,6 +17,8 @@
     "@tiptap/pm": "^2.27.2",
     "@tiptap/react": "^2.27.2",
     "@tiptap/starter-kit": "^2.27.2",
+    "html2canvas": "^1.4.1",
+    "jspdf": "^4.2.0",
     "marked": "^17.0.4",
     "react": "^19.1.0",
     "react-dom": "^19.1.0",