[OpenSpec] Unit Test Coverage 75%+ and Newman API Tests

[rubenvdlinde]

Goal

Bring Procest PHPUnit test coverage from ~26% to 75%+ and add Newman API tests.

Scope

Unit Tests Needed

Services (10 untested):

• NotificatieService
• ZgwBrcRulesService
• ZgwBusinessRulesService
• ZgwDocumentService
• ZgwDrcRulesService
• ZgwMappingService
• ZgwPaginationHelper
• ZgwRulesBase (via concrete subclass)
• ZgwService
• ZgwZtcRulesService

Controllers (11 untested):

• AcController
• BrcController
• DashboardController
• DrcController
• HealthController
• MetricsController
• NrcController
• SettingsController
• ZgwMappingController
• ZrcController
• ZtcController

Newman API Tests

• API workflow collections for ZGW endpoints
• Environment configuration for local dev

Acceptance Criteria

• Every PHP service has a unit test file with 3-5+ test methods
• Every PHP controller has a unit test file with 3-5+ test methods
• Newman collection covers main ZGW API workflows
• All tests pass via vendor/bin/phpunit
• File coverage >= 75% (33+ of 42 PHP files have tests)