More powerful Mac notifications and clearer version details

This update improves how Polymail integrates with macOS and makes it easier to understand what version you’re running:

• Richer macOS notifications: You can now take quick actions directly from notifications, including Reply, Mark as Read, and Delete, without opening the app.
• Clearer version info: The About dialog now shows the WebApp version more clearly, making it easier to reference when troubleshooting or sharing feedback.

These updates make Polymail feel faster and more native on macOS.