fix(doctrine): skip uninitialized properties in handleLazyObjectRelations

[marius-swfy]

Summary

• Add isInitialized() check before ReflectionProperty::getValue() in PersistProcessor::handleLazyObjectRelations() to prevent fatal errors on typed properties that are only set during Doctrine @PrePersist lifecycle callbacks.
• Since the method's purpose is to find lazy-loaded object relations, skipping uninitialized properties is safe — they cannot contain a lazy proxy object.

Test plan

• Added DummyWithUninitializedProperties fixture entity with typed properties without defaults
• Added testHandleLazyObjectRelationsSkipsUninitializedProperties test using Post(map: true) to exercise the canMap() code path with uninitialized typed properties
• All existing PersistProcessor tests continue to pass

Closes #7735

🤖 Generated with Claude Code

[soyuka]

Nice thanks!