Demo KG UI additions (WIP)

[caufieldjh]

This pull request introduces a new "Knowledge Graphs" feature to the application, integrating a knowledge graph catalog sourced from the KG-Registry project. The changes include backend service integration, controller and helper logic, new routes and navigation, and user interface components for browsing and viewing knowledge graphs and their details.

The most important changes are:

Knowledge Graphs Feature Implementation:

• Added a new KnowledgeGraphsController with index and show actions to support listing and viewing knowledge graphs, including filtering by query, category, status, and domain.
• Introduced a KgRegistry service to fetch, cache, and parse knowledge graph data from the KG-Registry YAML source, with support for local or remote loading and error handling.
• Created KnowledgeGraphsHelper with utility methods for formatting lists, dates, links, and contact values for display in the UI.

User Interface and Navigation:

• Added new HAML views for listing (index.html.haml) and showing (show.html.haml) knowledge graphs, including filter forms, detail tables, contact/curator cards, product and publication sections, and badges for metadata. [1] [2] [3]
• Updated the top navigation bar to include a "Knowledge Graphs" link for easy access to the new feature.
• Registered RESTful routes for knowledge_graphs#index and knowledge_graphs#show in routes.rb.

Documentation:

• Added a new Run_UI_Locally.md guide with instructions for running the UI locally using Docker Compose or a non-Docker Ruby/Rails setup.