feat: add Config tab to all node resource detail pages

[dtaniwaki]

resolves #581

Thanks for maintaining dbt-docs! I'd appreciate any feedback on this change.

Description

Currently there's no way to see a resource's dbt config directly in the docs UI. When working with engines like Athena, knowing partition and format settings (partitioned_by, file_format, etc.) is essential to writing efficient queries, but right now you have to go back to the YAML source to find them.

This PR adds a "Config" tab to all node-type detail pages that shows the full config in a structured, nested format. The tab only appears when config data exists, so macro pages are unaffected. Nested values like contract and docs render hierarchically, and null/empty entries are filtered out.

I extracted the data transformation logic into a testable config_utils.js module with 29 unit tests. All existing tests continue to pass. Tested locally against the jaffle_shop sample data.

Checklist

• I have read the contributing guide and understand what's expected of me
• I have signed the CLA
• I have run this code in development and it appears to resolve the stated issue
• I have opened an issue to add/update docs, or docs changes are not required/relevant for this PR
• I have run changie new to create a changelog entry