Keep Version importable in slim installations

[cdeil]

Summary

• defer model and model-processing imports in roboflow.core.version until the corresponding feature is used
• add a direct Version import to the existing slim compatibility suite

Motivation

A clean roboflow-slim installation currently cannot import Version:

from roboflow.core.version import Version

The import reaches full-SDK model helpers at module scope and fails successively on optional dependencies such as Pillow, pillow-avif-plugin, and packaging. Those helpers are only needed by specific model, training, deployment, or export paths.

Deferring them to those paths keeps the normal full-SDK behavior while making the core version API usable with the dependencies declared by the slim distribution.

Test plan

• full Python 3.14 suite: 971 passed, 1 skipped
• slim compatibility suite on Python 3.10: 51 passed
• slim compatibility suite on Python 3.14: 51 passed
• built roboflow-slim wheel imports Version with Pillow, AVIF, OpenCV, NumPy, Matplotlib, and packaging absent
• Ruff format/lint and mypy pass
• git diff --check origin/main...HEAD