Implement ResourcePort interface for polymorphic resource management

[jhw-db]

Implement ResourcePort interface to enable generic resource selection strategies.

Interface:

• get_available_capacity() -> float
• get_queue_length() -> int

Implementations:

• Workshop entity implements ResourcePort
• Enables polymorphic resource selection

Benefits:

• Polymorphic resource management
• Reusable selection strategies
• Type-safe resource operations