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/cubecl.rs

@@ -0,0 +1,17 @@
+//! CubeCL kernel tests.
+
+#[cfg(feature = "cube")]
+#[path = "."]
+mod cube {
+    type FloatElemType = f32;
+    type IntElemType = i32;
+
+    mod backend {
+        include!("common/backend.rs");
+        pub type ReferenceBackend = burn_ndarray::NdArray<FloatElemType>;
+    }
+    pub use backend::*;
+
+    #[path = "cubecl/mod.rs"]
+    mod kernel;
+}