task: #3620963 Set the recipe version to 1.0.0-alpha3

Closes #3620963

Sets the recipe version for the Educare 1.0.0-alpha3 release, off the 1.0.x tip ca8fa17d, whose pipeline 944934 is green on all 23 jobs.

Changes

• composer.json: version 1.0.x-dev -> 1.0.0-alpha3.
• README.md: the Educare shield badge and its ?ref= moved from 1.0.0-alpha2 to 1.0.0-alpha3.
• CHANGELOG.md: the 1.0.0-alpha3 entry, plus the [Unreleased] and [1.0.0-alpha3] compare links.

No dependency constraint changed: 1.0.x already carries zero x-dev requires, and drupal/vartheme_bs5_educare: ~1.0.0 resolves to the released 1.0.0-alpha5.

Release contents

• refactor: #3618244 Remove the Varbase Patches requirement and the Drupal CMS wiring script from the recipe
• feat: #3620058 Re-export the Canvas component configs for the Canvas Icon Picker
• task: #3620242 Move Search after Varbase Content Base in recipe.yml
• task: #3620331 Remove drupal/varbase_dev_base from composer.json: a development recipe that is required but never applied
• task: #3620349 Remove the dead drupal-libraries-sync.js script
• task: #3620438 Pin block component versions to active, so a stale hash cannot 500 the Canvas pages

AI-Generated: Yes

Checkpoints

• The version, badge and changelog all read 1.0.0-alpha3
• composer.json still parses, and all 35 requires are unchanged
• The base commit's pipeline is green (944934, 23/23, nothing allow_failure)
• No x-dev constraint remains in composer.json
• AI assistance disclosed in the commit message and here
• This merge request's own pipeline is green
• Reviewed by a human
• Code review by maintainers