Refactor environment and configuration management

- Updated the project structure to store configuration files (.env, models.yaml, extensions.yaml) in the project root instead of the user's home directory.
- Enhanced the setup process to automatically copy example files to the project root on first run.
- Implemented a migration function to transfer legacy configuration files from the user's home directory to the new project structure.
- Revised documentation to reflect changes in file locations and setup instructions.
- Improved code readability and maintainability by refactoring path management functions.

.gitignore

@@ -2,6 +2,8 @@
 .env
 .env.*
 !.env.example
+models.yaml
+extensions.yaml
 
 # SwarmUI checkpoints / LoRA dropped into the app tree
 Models/**
@@ -27,7 +29,7 @@ __pycache__/
 dist/
 *.egg-info/
 
-# Local CLI state (if someone runs from the repo)
+# Local CLI state / SSH key (inside the repo, not under %)
 .gpu-rent/
 .pytest_cache/
 .mypy_cache/