docs: add SQLite testing badge to README

- Add SQLite badge to highlight support for SQLite-based testing
- Reflects the recent CI improvements with faster SQLite tests
- Improves documentation clarity about testing capabilities

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: heysamtexas

README.md

@@ -5,6 +5,7 @@
 ![Django](https://img.shields.io/badge/Django-5.2.3-green.svg)
 ![Python](https://img.shields.io/badge/Python-3.12-blue.svg)
 ![PostgreSQL](https://img.shields.io/badge/PostgreSQL-16-blue.svg)
+![SQLite](https://img.shields.io/badge/SQLite-Testing-lightblue.svg)
 ![License](https://img.shields.io/badge/License-MIT-yellow.svg)
 ![Tests](https://img.shields.io/badge/Tests-Passing-brightgreen.svg)
 ![Ruff](https://img.shields.io/badge/Linting-Ruff-purple.svg)