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>

tests/test_web_db.py

@@ -1,5 +1,5 @@
 """
-Tests for web/db.py — user store and refresh token management.
+Tests for web/db.py - user store and refresh token management.
 """
 
 import pytest