Small update on Notes App

I improved some basic functions and also added some new features to the Notes app.

• Download as .txt: Replaced the old Save-to-filesystem button with a direct browser download that saves notes as plain .txt files.
• Status bar: Added a status bar at the bottom of the app that indicates current cursor position (Ln/Col) and live word count.
• GUI cleanup: Removed placeholder text, increased the default window size, and cleaned up the toolbar.