Rename to stealergram, add pyproject.toml, purge em-dashes

- Rename project to stealergram throughout
- Add pyproject.toml (replaces requirements.txt split, folds pytest.ini)
- Replace all em-dashes with hyphens across all source files

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web/routes/users.py

@@ -1,5 +1,5 @@
 """
-web/routes/users.py — User CRUD (superadmin only).
+web/routes/users.py - User CRUD (superadmin only).
 
 GET    /users           → list all users
 POST   /users           → create a new user