Normalize test model setup patterns across integration tests

[spawnia]

Summary

• unify factory/model setup patterns to prefer explicit attribute assignment over create array payloads
• normalize relation wiring to explicit associate plus save where applicable
• align setup readability by separating distinct model setup blocks consistently
• apply these updates across integration tests, including the earlier relation-delete regression areas and the remaining integration suite files

Validation

• run make
• all validation steps pass: rector, php-cs-fixer, prettier, phpstan, phpunit
• phpunit result: OK but there were issues (existing notices/skips/incomplete)