feat: add multiselect profile field type

[vitormattos]

Summary

• add backend support for new multiselect field type
• support multiselect values in personal settings and admin user dialog
• allow creating and editing multiselect definitions in admin catalog
• extend workflow checks to evaluate multiselect membership
• include updated screenshots generated from the app

Validation

• docker compose exec -u www-data nextcloud sh -lc 'cd /var/www/html/apps-extra/profile_fields && vendor/bin/phpunit -c tests/php/phpunit.xml tests/php/Unit/Service/FieldDefinitionValidatorTest.php tests/php/Unit/Service/FieldValueServiceTest.php tests/php/Unit/Workflow/UserProfileFieldCheckTest.php --no-coverage --colors=always'
• npm run ts:check
• npm run test
• docker compose exec -u www-data nextcloud sh -lc 'cd /var/www/html/apps-extra/profile_fields && composer cs:fix'
• docker compose exec -u www-data nextcloud sh -lc 'cd /var/www/html/apps-extra/profile_fields && composer psalm'

Screenshots (evidence)

Admin catalog

Personal settings

User management dialog