feat: add credits modal and update docker config

- Add credits modal showing project creators and libraries used
- Replace bottom-of-canvas credits with clickable credits button
- Update docker-compose to pull pre-built image from git.azuze.fr registry
- Simplify README Docker instructions

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

README.md

@@ -22,8 +22,7 @@ npm run dev  # Electron app
 
 **Docker:**
 ```bash
-npm run docker:build
-npm run docker:run  # http://localhost:8080
+docker-compose up  # http://localhost:8080
 ```
 
 Full build instructions (Windows installers, Linux AppImage/Flatpak) in [PACKAGING.md](PACKAGING.md).