feat: add unified linting scripts and git hooks for code quality enforcement

- Introduced `lint` and `lint-fix` applications in `flake.nix` for unified linting of backend (Python) and frontend (TypeScript/Svelte) code.
- Added `scripts/lint.sh` for manual linting execution.
- Created `scripts/install-hooks.sh` to set up git hooks for automatic linting before commits and optional tests before pushes.
- Updated `README.md` with instructions for using the new linting features and git hooks.

backend/app/core/errors.py

@@ -65,4 +65,3 @@ class UnsupportedFileTypeError(WebRefException):
     def __init__(self, file_type: str, allowed_types: list[str]):
         message = f"File type '{file_type}' not supported. Allowed types: {', '.join(allowed_types)}"
         super().__init__(message, status_code=415)
-