Replace `1.0-UNKNOWN` version string with less ambiguous `UNKNOWN`

Issue submitter TODO list

• I've searched for an already existing issues here
• I'm running a supported version of the application which is listed here and the feature is not present there

Is your proposal related to a problem?

https://github.com/kafbat/kafka-ui/blob/main/api/src/main/java/io/kafbat/ui/service/ReactiveAdminClient.java#L154

String version = "1.0-UNKNOWN";

The 1.0-UNKNOWN looks a bit ambiguous and confusing and people tend to be asking version of what it is:

Can this be changed to just UNKNOWN please? (not sure why Kafka-UI can't identify version of AWS MSK 🤷🏻)

Describe the feature you're interested in

Reduce ambiguity of unidentified cluster(?) version string.

Describe alternatives you've considered

No response

Version you're running

v1.1.0

Additional context

Let me know and I'll create a PR if this change isn't going to break something else (I'm a way not familiar with Java). Thank you.