Fix Gradle plugin resolution by removing dead JetBrains repo references

[Copilot]

Summary

Fix the PR build failures caused by stale JetBrains Space repository configuration that prevented Gradle from resolving required plugins.

Changes

• Removed dead JetBrains Space repository URLs from the root and build-logic Gradle settings
• Corrected the root buildscript repository/dependency block so it uses valid public repositories
• Kept the existing Dokka and plugin configuration intact with the public Gradle/Maven sources

Verification

• Reproduced the failure locally and confirmed the root cause was the invalid JetBrains Space repository configuration
• Updated the repository settings to use the standard public Gradle/Maven sources