feat: #3630126 Show users their own account details on their profile page

Issue: https://www.drupal.org/project/varbase_core/issues/3630126

• Adds a Varbase Core default recipe, recipes/default, applied from varbase_core_install() with RecipeRunner (the same pattern as Varbase Admin, Varbase Tour and Varbase Webform).
• The recipe ships the varbase_user_profile_details ECA model: a "Profile details" extra field (account owner only, varies by user) and a "User profile details" block, rendering the active theme's user-profile-details SDC. No action buttons: the user page keeps core's View / Edit tabs.
• The extra field is visible by default, so the shipped user display needs no change.
• New installs only: no update hook.

Pairs with https://www.drupal.org/project/vartheme_bs5/issues/3630125

How to test

1. Fresh install of Varbase 10.1.x with this branch and the Vartheme BS5 4.1.x branch.
2. Log in as a user with no extra role and visit /user: the Profile details card shows.
3. As an administrator, view that user's profile: no card.

Tested on a fresh Varbase 10.1.x DDEV install (Drupal 11.4.9).

AI-Generated: Yes. Developed with Claude Code assistance, human review pending.

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

🤖 Generated with Claude Code