chore: relicense under the GNU AGPLv3

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/components/AboutModal.tsx

@@ -5,7 +5,7 @@ import { ReadingModal } from './ReadingModal';
 
 // Project facts shown in "Über MindSift"; change here when the repository or license changes
 export const PROJECT_REPO_URL = 'https://git.dsit.me/sandrodach/MindSift';
-export const PROJECT_LICENSE = 'The Unlicense – gemeinfrei, ohne Bedingungen';
+export const PROJECT_LICENSE = 'GNU AGPLv3 – freie Software, Änderungen bleiben frei';
 
 export const AboutModal: React.FC<{ onClose: () => void }> = ({ onClose }) => (
   <ReadingModal title="Über MindSift" onClose={onClose}>