Check library versions

[DerrickYLJ]

Update pyproject.toml with correct and compatible dependency versions to enable environment recreation.

The previous pyproject.toml was incorrect. This update establishes core dependencies like transformers (>=4.52,<4.53) and torch (>=2.1,<2.6, with Flex Attention features optionally enabling >=2.5) based on API usage detected in the codebase (e.g., scaled_dot_product_attention, flex_attention, use_kernel_forward_from_hub). Optional dependency groups for experiments, Flash Attention, and development are also included.

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[cursor]

Cursor Agent can help with this pull request. Just @cursor in comments and I'll start working on changes in this branch.
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