refactor(connections)!: remove the clipboard banner and Copy as JSON

[datlechin]

Why

The New Connection form read the general pasteboard every time it opened, to offer a URL banner. On the macOS 27 SDK that programmatic read asks for permission. Share > Copy as JSON was a third way to serialize a connection, next to Copy Connection String and Copy TablePro Link.

Change

• Removed the clipboard URL banner from the New Connection form. Import from URL still fills the form from a pasted link.
• Removed Share > Copy as JSON from the connection list. The data grid's Copy as JSON stays.
• The banner's URL tests now run against Import from URL.

Not in this PR

• The Import from URL sheet still prefills from the pasteboard when it opens.