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/exp.rs

@@ -0,0 +1,29 @@
+use super::*;
+use burn_tensor::{TensorData, Tolerance};
+
+#[test]
+fn should_diff_exp() {
+    let data_1 = TensorData::from([[1.0, 7.0], [-2.0, -3.0]]);
+    let data_2 = TensorData::from([[4.0, -7.0], [2.0, 3.0]]);
+
+    let device = Default::default();
+    let tensor_1 = TestAutodiffTensor::<2>::from_data(data_1, &device).require_grad();
+    let tensor_2 = TestAutodiffTensor::from_data(data_2, &device).require_grad();
+
+    let tensor_3 = tensor_1.clone().matmul(tensor_2.clone().exp());
+    let grads = tensor_3.backward();
+
+    let grad_1 = tensor_1.grad(&grads).unwrap();
+    let grad_2 = tensor_2.grad(&grads).unwrap();
+
+    let tolerance = Tolerance::default();
+    let expected = TensorData::from([[54.5991, 27.4746], [54.5991, 27.4746]]);
+    grad_1
+        .to_data()
+        .assert_approx_eq::<FloatElem>(&expected, tolerance);
+
+    let expected = TensorData::from([[-5.4598e+01, -9.1188e-04], [2.9556e+01, 8.0342e+01]]);
+    grad_2
+        .to_data()
+        .assert_approx_eq::<FloatElem>(&expected, tolerance);
+}