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-backend-tests/tests/autodiff/bridge.rs

@@ -0,0 +1,27 @@
+use super::*;
+use burn_tensor::{DType, Distribution, Tensor};
+
+#[test]
+fn test_full_precision() {
+    let device = Default::default();
+    let x1 = Tensor::<TestAutodiffBackend, 2>::random([32, 32], Distribution::Default, &device)
+        .require_grad();
+    let x2 = Tensor::<TestAutodiffBackend, 2>::random([32, 32], Distribution::Default, &device)
+        .require_grad();
+    let dtype = x1.dtype();
+
+    let x3 = x1.clone().cast(DType::F32);
+    let x4 = x2.clone().cast(DType::F32);
+
+    let x5 = x3.matmul(x4);
+    let x6 = x5.cast(dtype);
+    let x7 = x6 * x1.clone() / x2.clone();
+
+    let grads = x7.backward();
+
+    let x1_grad = x1.grad(&grads);
+    let x2_grad = x2.grad(&grads);
+
+    assert!(x1_grad.is_some());
+    assert!(x2_grad.is_some());
+}