Rework Synchronization view

[fnune]

Problem

The Synchronization view tries to do too much: device pairing, sync status, and folder configuration all in one place. This makes it hard to use.

Proposed solution

• Upstream sync information into the Catalog view (folder sync status, size on disk, last synced date)
• Refocus Synchronization view as a setup and device pairing view
• Add notifications for sync events (sync started, completed, conflicts detected)

Alternatives considered

None.