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.rs

@@ -0,0 +1,20 @@
+//! Burn autodiff tests.
+
+#![allow(
+    clippy::single_range_in_vec_init,
+    clippy::duplicate_mod,
+    reason = "false positive"
+)]
+extern crate alloc;
+
+pub type FloatElemType = f32;
+#[allow(unused)]
+pub type IntElemType = i32;
+
+#[path = "common/backend.rs"]
+mod backend;
+pub use backend::*;
+
+#[allow(clippy::module_inception)]
+#[path = "common/autodiff.rs"]
+mod autodiff;