Add browser Python editor with Pyodide, user auth, and workspace API

- FastAPI serves static UI, file CRUD under code/ and read-only lib/
- Pyodide worker runs Python and Jedi completions in the browser
- SQLite accounts: login/register, session cookies, superuser user management
- Optional EDITOR_API_KEY, AUTH_* env vars, .env.example
- Pipenv, pytest, Selenium smoke test, README

Made-with: Cursor

pytest.ini

@@ -0,0 +1,4 @@
+[pytest]
+markers =
+    integration: browser / network integration tests
+    selenium: Selenium UI tests (need running server; see README)