PHP 8.2+ Strict Typing and Readonly Properties

Problem/Motivation

The module needs to be modernized to take full advantage of PHP 8.2 features, including strict typing and readonly properties, which improve code quality and performance.

Proposed resolution

• Add type hints to all class properties (e.g., protected EntityTypeManagerInterface $entityTypeManager).
• Add return type hints to all methods.
• Use readonly properties for services injected via the constructor where applicable.

Remaining tasks

Update all classes with modern PHP type hints.

User interface changes

None.

API changes

Strict typing added to method signatures.

Data model changes

None.