feat: #3613682 Add Varbase Events Base and render the event listings from the events view

Issue: #3613682 Add Varbase Events Base and render the event listings from the events view

What this changes

Events become content, from the base recipe. varbase_events_base is composed into the site template, so the Event content type, its fields (field_when, field_location, field_event_categories, field_description, field_featured_image, body), the Event categories vocabulary, the events view and the Drupal Canvas templates all come from the base recipe. Nothing about an event is redefined here.

The listings follow the content. The Events page was rendering the blog view; it now renders the events view with its exposed filter. The three hand-placed cards on the Home page, which all read "Digital Security for Advocacy Groups", are replaced by the same view.

Rendered through the site theme. The events view and both event Canvas templates are repointed with setViewsComponentStyleTheme and repointComponentTreeToTheme. Without this the view binds its component style to stark and every listing fails with Unable to find component "stark:views-view-grid".

Three demo events with their categories, dates and locations: a webinar, a policy briefing and a summit.

How this was verified

• drush site:install recipes/horizonaid from a dropped database: exit code 0, no error lines.
• /events and the Home "Upcoming Events" section each render three event rows, counted from the rendered /events/<name> links.
• /, /about, /resources, /programs, /events, /countries, /donate, an event page and a country page all return 200 with no Twig LoaderError and no ComponentNotFoundException.
• Content after install: 12 countries, 3 events, 3 blog posts.
• gitlab-ci-local runs the project pipeline green (build:composer-validate, validate:yaml-lint).

User interface changes

• An Event content type is available, and events are published under /events/.
• The Events page and the Home "Upcoming Events" section follow the content instead of hand-placed cards.

API changes

None.

Data model changes

• The Event content type, its fields and the Event categories vocabulary come from varbase_events_base.

Release notes snippet

• Added Varbase Events Base with three demo events, and moved the event listings onto the events view.

AI-Generated: Yes

Checkpoints

• 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
• Reviewed by a human
• Code review by maintainers
• Full testing and approval
• Credit contributors
• Review with the product owner
• Update Release Notes
• Release