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_database.py

@@ -1,5 +1,5 @@
 """
-Tests for utils/database.py — SQLite persistence layer.
+Tests for utils/database.py - SQLite persistence layer.
 
 Each test gets an isolated in-memory-equivalent DB via the `isolated_db`
 fixture so tests never touch data/hits.db.
@@ -112,7 +112,7 @@ def test_by_severity_returns_correct_severity():
 
 
 def test_by_severity_excludes_duplicates():
-    """seen_before=1 rows must be invisible to by_severity — they are stored for stats only."""
+    """seen_before=1 rows must be invisible to by_severity - they are stored for stats only."""
     hit = make_hit(severity=HIGH, url="intranet.testcorp.com")
     db_module.insert_hits([hit], source="c", filename="f.txt", seen_before=True)
     assert db_module.by_severity(HIGH) == []