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

.gitignore

@@ -1,8 +1,10 @@
 # Rust build artifacts
 target/
+
+# Cargo lock file
 Cargo.lock
 
-# Rust IDE files
+# IDE files
 .vscode/
 .idea/
 
@@ -131,3 +133,13 @@ demo/
 
 # Additional Rust specific
 *.lock
+
+# Generated model files
+*.mpk
+*.pt
+*.bin
+*.safetensors
+*.ckpt
+
+# User-specific data
+user_data/