Apply factory pattern to C code

Encapsulate C object allocation and initialization

Centralizing object creation logic and enabling dependency injection at construction.

• · allocation strategy (heap/stack)
• · init parameters

• · initialized struct pointer or value

Caller ownership model defined

Uninitialized fields, memory leak on error, ik_env_t unavailable

• · ik_env_t convention
• · ik_*_create() naming