Add legal disclaimer for catalog page

What does this MR do and why?

This MR adds a legal disclaimer to the header of the CI/CD catalog page. The disclaimer should only be visible on GitLab.com.

References

Please include cross links to any resources that are relevant to this MR. This will give reviewers and future readers helpful context to give an efficient review of the changes introduced.

• #550745 (internal link)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

GitLab.com	other

How to set up and validate locally

1. Create a new project for your CI/CD component

2. Set up the component structure Create the following files in your test project:

   template.yml (CI/CD component template):

   spec:
     inputs:
       stage:
         default: test
         description: Pipeline stage
       image:
         default: alpine:latest
         description: Docker image to use
   
   ---
   
   lint-markdown:
     stage: $[[ inputs.stage ]]
     image: $[[ inputs.image ]]
     script:
       - echo "Running markdown lint"
       - echo "Component: $CI_PROJECT_PATH"

   README.md:

   # Test Component
   
   This is a test CI/CD component for validating breadcrumb functionality.
   
   ## Usage
   
   ```yaml
   include:
     - component: gitlab.example.com/root/test-component@main
       inputs:
         stage: validate

3. Publish the component to the catalog

4. Visit Explore -> CI/CD catalog and verify the legal disclaimer.

5. Use this guide to simulate a SAAS instance

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #550745