Add MIT License and update README with license badge

Author: nim444

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2025
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

@@ -6,6 +6,7 @@
 [![Code style: ruff](https://img.shields.io/endpoint?url=https://raw.githubusercontent.com/astral-sh/ruff/main/assets/badge/v2.json)](https://github.com/astral-sh/ruff)
 [![Tests passing](https://img.shields.io/badge/Tests-passing-brightgreen.svg)](#running-tests)
 [![Coverage: 100%](https://img.shields.io/badge/Coverage-100%25-brightgreen.svg)](https://codecov.io/gh/nim444/fastapi-auth-multi-db) <!-- Assuming Codecov is setup -->
+![MIT License](https://img.shields.io/badge/License-MIT-green.svg)
 
 A robust FastAPI application demonstrating user registration, JWT authentication (including refresh tokens), and a flexible repository pattern supporting SQLite, PostgreSQL, and MongoDB backends.
 
@@ -18,7 +19,6 @@ This project serves as a template or starting point for building secure and scal
 * **Modern Tooling:** Utilizes `uv` for dependency management, `Dynaconf` for configuration, and `ruff` for linting/formatting.
 * **Testability:** Designed with dependency injection and includes a comprehensive test suite using `pytest`.
 
-
 ## User Interface
 
 Below is a preview of the application's interface:
@@ -37,7 +37,6 @@ Below is a preview of the application's interface:
 * Comprehensive test suite with `pytest` (including coverage).
 * Health check endpoint (`/health`).
 
-
 ## Architecture Diagram
 
 Below is an overview of the application's architecture: