docs: add GPL v3 license and AI attribution section to all READMEs

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

README.md

@@ -14,6 +14,7 @@
 ![SQLite](https://img.shields.io/badge/SQLite-003B57?logo=sqlite&logoColor=white)
 ![Nginx](https://img.shields.io/badge/Nginx-009639?logo=nginx&logoColor=white)
 ![Docker](https://img.shields.io/badge/Docker-2496ED?logo=docker&logoColor=white)
+[![License: GPL v3](https://img.shields.io/badge/License-GPLv3-blue.svg)](LICENSE)
 
 </div>
 
@@ -285,3 +286,20 @@ npm run dev   # Vite dev server on :5173, proxies /api/ to :8000
 ## 🏗️ Architecture
 
 See [`docs/architecture.md`](docs/architecture.md) for the detailed request flow, Docker setup, and authentication model.
+
+---
+
+## 🤖 Built with AI assistance
+
+This application was developed entirely with the help of AI coding assistants:
+
+- **[Claude Code](https://claude.ai/code)** (Anthropic) — used throughout the project for architecture design, backend API (FastAPI, SQLAlchemy, authentication, ICMP discovery), frontend components (Vue 3, CSS topology layout, i18n, dark mode), Docker & Nginx configuration, and documentation.
+- **[Codex](https://openai.com/codex)** (OpenAI) — also used during development for code generation and suggestions across the entire codebase.
+
+---
+
+## 📄 License
+
+This project is licensed under the [GNU General Public License v3.0](LICENSE).
+
+You are free to use, modify and distribute this software under the terms of the GPL v3. Any derivative work must be distributed under the same license.