ManuNotes for iOS 0.3.0

Simulator-only build. This does not install on a physical iPhone — that needs a paid Apple Developer Program enrollment (ad-hoc export or TestFlight), not yet active for this project. Unzip and drag ManuNotes.app onto a running iOS Simulator window, or xcrun simctl install <device> ManuNotes.app.

Added

• Per-note export. Both the note editor's menu and the notes list's
  card context menu now offer Markdown/Plain Text/Sticky Archive export
  for a single note, named after its title instead of the bulk export's
  generic "Notes.md".
• About screen, reachable from the export/import menu: app icon,
  name, developer credit, and version/build.