Check traversal id searchable on only ready zoekt repos

What does this MR do and why?

Check traversal id searchable on only ready zoekt repos

AI Summary

This change modifies how the system checks database schema versions when deciding whether to use a specific type of search query.

Previously, the code looked at all repositories to find the minimum schema version. Now it only considers "ready" repositories - filtering out any that might be in an incomplete or problematic state.

The test code was also updated to be cleaner and more organized. Instead of setting up mock responses in each individual test, the setup is now centralized at the top level, and one test case was restructured to be more readable by grouping related logic together.

This change helps ensure the system makes decisions based only on repositories that are actually available and functioning properly, rather than potentially being influenced by repositories that aren't ready for use.

References

Related to #561000 (closed)

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Before	After

How to set up and validate locally

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