feat: update workspace paths and enhance gitignore

- Updated stablediffusion crate path from "../stable-diffusion-burn" to "./crates/stable-diffusion-burn" for proper workspace resolution
- Enhanced .gitignore to include generated model files (.mpk, .pt, .bin, .safetensors, .ckpt) and user_data directory
- Added Cargo.lock to gitignore with appropriate comment
- Reorganized IDE files section in gitignore for better clarity
- Added newline at end of file for proper formatting

crates/stable-diffusion-burn/burn-crates/burn-cuda/README.md

@@ -0,0 +1,30 @@
+# Burn CUDA Backend
+
+[Burn](https://github.com/tracel-ai/burn) CUDA backend
+
+[![Current Crates.io Version](https://img.shields.io/crates/v/burn-cuda.svg)](https://crates.io/crates/burn-cuda)
+[![license](https://shields.io/badge/license-MIT%2FApache--2.0-blue)](https://github.com/tracel-ai/burn-cuda/blob/master/README.md)
+
+This crate provides a CUDA backend for [Burn](https://github.com/tracel-ai/burn) using the
+[cubecl](https://github.com/tracel-ai/cubecl.git) and [cudarc](https://github.com/coreylowman/cudarc.git)
+crates.
+
+## Usage Example
+
+```rust
+#[cfg(feature = "cuda")]
+mod cuda {
+    use burn_autodiff::Autodiff;
+    use burn_cuda::{Cuda, CudaDevice};
+    use mnist::training;
+
+    pub fn run() {
+        let device = CudaDevice::default();
+        training::run::<Autodiff<Cuda<f32, i32>>>(device);
+    }
+}
+```
+
+## Dependencies
+
+Requires CUDA 12.x to be installed and on the `PATH`.