fix(connection): disconnect all connections on VS shutdown

[CalvinAllen]

Problem

When Visual Studio closes, active Couchbase connections are not properly disposed. The Package.Dispose() method only disposes the editor factory, leaving cluster connections orphaned.

Solution

Add a DisconnectAll() method to CouchbaseService and call it from Package.Dispose() to properly clean up all active connections on shutdown.

Acceptance Criteria

• Add CouchbaseService.DisconnectAll() method
• Call DisconnectAll() from CouchbaseExplorerPackage.Dispose()
• All ICluster instances properly disposed on VS exit
• No orphaned network connections