fix(migration): shorten index name for DB compatibility

[vitormattos]

Summary

• shorten the index identifier for (active, sort_order) in migration Version1000Date20260309120000
• prevents installation failure on DB engines with stricter identifier length limits

Validation

• docker compose exec -u www-data -w /var/www/html/apps-extra/profile_fields nextcloud composer cs:fix
• docker compose exec -u www-data -w /var/www/html/apps-extra/profile_fields nextcloud composer psalm
• docker compose exec -u www-data -w /var/www/html/apps-extra/profile_fields nextcloud composer test:unit
• docker compose exec -u www-data -w /var/www/html/apps-extra/profile_fields nextcloud composer test:php:controller-integration

Closes #65