Update LICENSE badge in README.md to AGPLv3 from MIT

[chigwell]

User Story
As a maintainer,
I want the LICENSE badge in README.md to reflect the project’s actual AGPLv3 license
so that contributors and users avoid compliance risks and confusion.

Background
The repository’s LICENSE file contains the GNU AGPLv3 license, but the README.md displays an MIT license badge. This mismatch creates ambiguity about legal obligations, particularly for downstream users or contributors who might assume MIT terms apply. The inconsistency occurs in:

• README.md: Line 2 shows [![License: MIT](https://img.shields.io/badge/License-MIT-green.svg)](https://opensource.org/licenses/MIT)
• LICENSE: Full AGPLv3 text confirms the correct license.

This discrepancy could lead to unintentional violations of AGPLv3 requirements, such as failing to disclose modified source code when deploying networked services.

Acceptance Criteria

• Modify README.md to replace the MIT badge with the AGPLv3 badge using the markdown:
  [![License: AGPLv3](https://img.shields.io/badge/License-AGPLv3-blue.svg)](https://www.gnu.org/licenses/agpl-3.0)
• Confirm the badge URL points to the AGPLv3 license documentation.
• Verify the badge displays correctly in rendered README previews.
• Ensure no other references to MIT exist in documentation (e.g., setup.py correctly specifies AGPLv3).
• Validate the LICENSE file remains unchanged and matches AGPLv3 terms.