Add Enum support

[pbedn]

Summary

• implement Python-style Enum classes
• generate typedef enum in C output
• export enum members from modules
• parse, typecheck and compile enums
• add stdlib marker class Enum
• test parser, type checker, module loader, codegen, pipeline

Testing

• pytest -q

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https://chatgpt.com/codex/tasks/task_e_6885d49a5fcc83219c9f07a27242e87e