Initialize Varbase Demo Content recipe for Varbase evaluation and testing

Problem/Motivation

New Varbase installations need demo content to showcase features and provide a working starting point for evaluation. Currently, demo content is provided through the varbase_demo module, but this approach doesn't align with modern Drupal's recipe-first architecture.

We need a standalone recipe that provides demo content for Varbase sites, making it easier for users to:

• Evaluate Varbase features and capabilities
• Get a working starting point with sample blog posts
• See how Varbase integrates with Drupal CMS blog functionality
• Test and demonstrate Varbase without committing to production content

Proposed resolution

• Provides 12 sample blog posts with featured images, tags, and descriptions
• Includes 28 taxonomy terms (blog tags and categories)
• Uses the standard Drupal CMS - Byte "blog" content type
• Depends on Varbase Media Assets recipe for demo media files
• Follows Drupal CMS recipe patterns and structure
• Contains only content files (no config) for maximum flexibility

Remaining tasks

• ✅ File an issue about this project
• ✅ Addition/Change/Update/Fix to this project
• ✅ Testing to ensure no regression
• ✅ Automated unit/functional testing coverage
• ➖ Developer Documentation support on feature change/addition
• ➖ User Guide Documentation support on feature change/addition
• ➖ UX/UI designer responsibilities
• ✅ Accessibility and Readability
• ✅ Code review from 1 Varbase core team member
• ✅ Full testing and approval
• ✅ Credit contributors
• ✅ Review with the product owner
• ✅ Update Release Notes
• ❌ Release varbase-11.0.0-alpha1, varbase_starter-1.0.0-alpha1, varbase_demo_content-1.0.0-alpha1

User interface changes

• N/A

API changes

• N/A

Data model changes

• N/A

Release notes snippet

• feat: #3570169 Initialize Varbase Demo Content recipe for Varbase evaluation and testing