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>

utils/database.md

@@ -85,5 +85,5 @@ Indexes: `url`, `username`, `source`, `timestamp`, `severity`.
 ## Notes
 
 - Each query opens and closes its own connection via the `_connect()` context manager.
-- `conn.row_factory = sqlite3.Row` — rows support both index and column-name access.
+- `conn.row_factory = sqlite3.Row` - rows support both index and column-name access.
 - Transactions: commit on success, rollback on exception.