nermal v0.1.1

Add update checker, fix sidebar scroll, bump version to 0.1.1

- Add lightweight update checker: compares the running app version
  against the latest GitHub release and shows a dismissible banner
  plus a manual check in Settings > About. Uses tauri-plugin-opener
  to open the release page in the system browser.
- Fix sidebar note list not scrolling and colliding with the
  Settings button: the scrollable container had no height
  constraint against its flex parent.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>