PHPStan: infer targetEntity from property type for ManyToOne associations

[JanTvrdik]

Summary

• Extends PHPStan type inference to work for ManyToOne associations without explicit targetEntity attribute
• Previously only OneToOne associations could infer target entity from property type
• Adds test entities and test cases to verify the fix (reproduces issue PHPStan rules not working correctly? #37)

Problem

When using associations without explicit targetEntity attribute:

#[ManyToOne(inversedBy: 'subordinates')]
public ?Employee $supervisor = null;

PHPStan would incorrectly report: "Property 'Employee::$supervisor' is not a valid Doctrine association."

Solution

Extended the getAssociationTargetTypeFromPropertyReflection method to also infer target entity from property type for ManyToOne associations, not just OneToOne.

Test plan

• Added Employee and EmployeeSettings test entities replicating issue PHPStan rules not working correctly? #37
• Added test cases for associations without explicit targetEntity
• All PHPStan integration tests pass (both with and without phpstan-doctrine)
• All unit tests pass
• PHPStan analysis passes
• Code style checks pass

Fixes #37

[janedbal]

Or, we might drop this fallback completely to mitigate all maintenance. And only support PHPStan inference when phpstan-doctrine is used properly.