feat: add type stubs for cli, codegen, and security modules

openapi_first/codegen.pyi

@@ -0,0 +1,11 @@
+from pathlib import Path
+
+from .codegen_routes import generate_routes
+
+def generate_models(
+    spec_path: Path,
+    output_path: Path,
+    pydantic_version: int = ...,
+) -> None: ...
+
+__all__ = ["generate_models", "generate_routes"]