feat: #3628552 Apply the Varbase AI Context and Varbase AI Safety recipes with the Varbase AI Base recipe

Issue: https://www.drupal.org/project/varbase_ai_base/issues/3628552

• Add varbase_ai_context, then varbase_ai_safety last, to recipes:.
• README: "Included Sub-Recipes" now matches recipes:, with a note that Safety needs a default AI chat model.
• CHANGELOG entry under Unreleased. No version bump.

Tested on a fresh Varbase 11 site (core 11.4.8). With a default chat model it applies fully: 3 context items, 14 guardrails in 3 sets, AI Logging and AI Observability. With no provider reachable (amazee.ai blocked, no key) it stops with The operation type 'chat' does not have a default model, before the base's own install: and config actions.

AI-Generated: Yes

Checkpoints:

• File an issue
• Addition/Change/Update/Fix
• Testing to ensure no regression
• Automated unit testing coverage
• Automated functional testing coverage
• UX/UI designer responsibilities
• Readability
• Accessibility
• Performance
• Security
• Developer Documentation
• User Guide Documentation
• Reviewed by human
• Code review by maintainers
• Full testing and approval
• Credit contributors
• Review with the product owner
• Release notes snippet
• Release