feat: Add macOS compatibility fixes

- Change PyTorch dependency from CUDA to CPU version for macOS support
- Update Rust edition from 2024 to 2021 for stable Cargo compatibility
- Relax PyTorch version requirement from >=2.8.0 to >=2.0.0
- Update dependency lock file with compatible versions

pyproject.toml

@@ -13,7 +13,7 @@ dependencies = [
     "regex>=2025.9.1",
     "tiktoken>=0.11.0",
     "tokenizers>=0.22.0",
-    "torch>=2.8.0",
+    "torch>=2.0.0",
     "transformers>=4.0.0",
     "uvicorn>=0.36.0",
     "wandb>=0.21.3",
@@ -23,15 +23,15 @@ dependencies = [
 requires = ["maturin>=1.7,<2.0"]
 build-backend = "maturin"
 
-# target torch to cuda 12.8
+# target torch to cpu/mps for macOS
 [tool.uv.sources]
 torch = [
-    { index = "pytorch-cu128" },
+    { index = "pytorch-cpu" },
 ]
 
 [[tool.uv.index]]
-name = "pytorch-cu128"
-url = "https://download.pytorch.org/whl/cu128"
+name = "pytorch-cpu"
+url = "https://download.pytorch.org/whl/cpu"
 explicit = true
 
 [tool.maturin]

rustbpe/Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "rustbpe"
 version = "0.1.0"
-edition = "2024"
+edition = "2021"
 
 [dependencies]
 dary_heap = "0.3"