Enhance coding guidelines in .cursor/rules/coderule.mdc and .cursor/rules/python.mdc

- Added a guideline to place all source code under the `src/` directory in `coderule.mdc`.
- Removed the outdated guideline regarding the `src/` layout in `python.mdc` to streamline project structure.

These updates improve project organization and maintainability by clarifying the structure for source code and project files.

.cursor/rules/python.mdc

@@ -8,7 +8,6 @@ globs: ["**/*.py", "**/pyproject.toml", "**/requirements*.txt"]
 - Use type hints on all function signatures; validate with `mypy` or `pyright`
 - Use `pydantic` for data validation and serialization
 - Import order: stdlib -> third-party -> local; use absolute imports
-- Use `src/` layout to separate app code from project files
 - Use context managers (`with`) for resource management
 - Catch specific exceptions, never bare `except:`; use custom exception classes
 - Use `async`/`await` with `asyncio` for I/O-bound concurrency