fix: Resolve the PHPStan findings raised by the updated analyzers

Problem/Motivation

The phpstan CI job fails on the 2.0.x branch: the updated phpstan-drupal analyzers raise drupal.entityStorageDirectInjection and drupal.entityStoragePropertyAssignment on the pre-existing user-storage injection in src/Plugin/Block/VarbaseDashboardUser.php.

Steps to reproduce

Run the phpstan job on the branch pipeline.

Proposed resolution

• Inject the entity type manager instead of a storage handler and resolve the user storage at use time.

Remaining tasks

• ✅ 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

User interface changes

• N/A

API changes

• N/A

Data model changes

• N/A

Release notes snippet

• The user dashboard block now injects the entity type manager.

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