nix: add pyright/ruff for proper LSP in the impure devshell (#2496)

We need this to ensure that pyright/ruff are part of the same
interpreter/venv.

flake.nix

@@ -82,8 +82,10 @@
                 docker
                 pip
                 ipdb
+                pyright
                 pytest
                 pytest-asyncio
+                ruff
                 syrupy
               ]);