[Enhancement]: Request to implement custom agent categories in Agent Marketplace

[Educg550]

What features would you like to see added?

As described in issue #9287, I want to implement the custom agent categories feature by getting a list of categories in librechat.yaml. Following is an example of how should it look like:

# Categories configuration for organizing agents in Agent Marketplace
categories:
  disableDefaultCategories: false  # Option to disable default categories
  list:
    - value: "Productivity"
      description: "Agents to help boost your productivity."
    - value: "Education"
      description: "Educational agents for learning and research."
    - value: "Health & Wellness"
      description: "Agents focused on health and wellness topics."

Implementation notes

• If librechat.yaml contains categories, it will apply the settings as the above example suggests.
• The implementation will affect the backend YAML config loading function only.
• This setting is completely optional and nothing will break because the categories setting is not set in librechat.yaml

Code of Conduct

• I agree to follow this project's Code of Conduct