v1.1

Changes

• fix(signer): Fix empty signature appearance in signed PDFs
  • Replace direct layer0 canvas drawing with setSignatureGraphic API
  • Add explicit Helvetica font for layer2 text rendering
  • Extract signer CN from certificate for display
  • Use unique timestamp-based field names for multiple signatures support
• refactor: Apply CLAUDE.md code quality audit fixes
• chore: Add signature.png to gitignore