Failures to set the `server-url` in the setup flow are ignored

[richard-cox]

Setup

• Rancher version: v2.12

Describe the bug

• during the setup flow we apply the setting server-url
• failures though are ignored and the user is progressed to the home page

To Reproduce

• Possible - supply invalid characters
• Code - just break the url
• Tricky - create a custom role that allows access to the page but not to change settings

Result

• user is taken to home page

Expected Result

• user is informed of error
• tbd - what to do with fields related to parts that succeeded?