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/flip.rs

@@ -0,0 +1,29 @@
+use super::*;
+use burn_tensor::TensorData;
+use burn_tensor::Tolerance;
+
+#[test]
+fn should_diff_flip() {
+    let data_1 = TensorData::from([[[1.0, 7.0], [2.0, 3.0]]]); // 1x2x2
+    let data_2 = TensorData::from([[[3.0, 2.0, 7.0], [3.0, 3.2, 1.0]]]); // 1x2x3
+
+    let device = Default::default();
+    let tensor_1 = TestAutodiffTensor::<3>::from_data(data_1, &device).require_grad();
+    let tensor_2 = TestAutodiffTensor::from_data(data_2, &device).require_grad();
+
+    let tensor_3 = tensor_2.clone().flip([1, 2]);
+    let tensor_4 = tensor_1.clone().matmul(tensor_3);
+    let grads = tensor_4.backward();
+
+    let grad_1 = tensor_1.grad(&grads).unwrap();
+    let grad_2 = tensor_2.grad(&grads).unwrap();
+
+    let tolerance = Tolerance::default().set_half_precision_relative(1e-3);
+    grad_1
+        .into_data()
+        .assert_approx_eq::<FloatElem>(&TensorData::from([[[7.2, 12.0], [7.2, 12.0]]]), tolerance); // 1x2x2
+    grad_2.into_data().assert_approx_eq::<FloatElem>(
+        &TensorData::from([[[10.0, 10.0, 10.0], [3.0, 3.0, 3.0]]]),
+        tolerance,
+    ); // 1x2x3
+}