update phpstan to 2.0 and fix errors it reports

[tacman]

Updated PHPStan from 1.x to 2.0 and resolved all resulting analysis errors.

Tests pass.

Composer Updates

• phpstan/phpstan: ^1.2 → ^2.0
• phpstan/phpstan-phpunit: ^1.0 → ^2.0
• phpstan/phpstan-symfony: ^1.0 → ^2.0
• phpstan/extension-installer: kept at ^1.4 (not yet available as 2.0)

Config Changes

• Removed deprecated PHPStan options from phpstan.neon:
  • checkMissingIterableValueType
  • checkGenericClassInNonGenericObjectType
• Added ignoreError for property.onlyRead in test fixtures (Doctrine-managed entity IDs)

Code Fixes

Source code:

• TimestampableCacheClearer: Removed nullable type from property (never assigned null)
• Configuration: Added PHPDoc type hints for array parameters/return types
• EntityConfiguration: Added PHPDoc type hint for array parameter
• TimestampableEventSubscriber: Fixed generic type annotation
  Test code:
• Address, Organization: Changed ?int to int, added @readonly PHPDoc
• FunctionalTestCase: Fixed method_exists() call, used list<> type
• MappingTest: Fixed generic type annotation
• All test classes with createKernel(): Added @param array<string, mixed> $options PHPDoc