Feature: New account setup wizard

The account setup wizard was completely redesigned. The new wizard uses
a modern step-by-step flow with WebFinger-based server discovery,
improved error handling, and a configurable branded appearance including
themed logos and colors.

https://github.com/owncloud/client/pull/12189
https://github.com/owncloud/client/pull/12203
https://github.com/owncloud/client/pull/12212
https://github.com/owncloud/client/pull/12213
https://github.com/owncloud/client/pull/12216
https://github.com/owncloud/client/pull/12221
https://github.com/owncloud/client/pull/12226
https://github.com/owncloud/client/pull/12233
https://github.com/owncloud/client/pull/12235
https://github.com/owncloud/client/pull/12237
https://github.com/owncloud/client/pull/12277
