add composer-unused, comprehensive docs, and project restructure

- Add icanhazstring/composer-unused as dev dependency for dependency hygiene checks
- Add German documentation (docs/) covering architecture, conventions, workflows, and developer checklists
- Add API layer (ApiAuth, ApiBootstrap, ApiResponse), audit, scheduler, custom fields, and SSO services
- Add Microsoft OIDC SSO, API token management, and user lifecycle features
- Add swagger-ui vendor integration and OpenAPI spec
- Add production Docker setup and bin/ scripts
- Update composer dependencies, config, templates, and frontend assets throughout

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

docker-compose.yml

@@ -21,6 +21,22 @@ services:
       - db
       - memcached
 
+  scheduler:
+    build:
+      context: .
+      dockerfile: docker/php/Dockerfile
+    env_file:
+      - .env
+    environment:
+      APP_DEBUG: "0"
+    volumes:
+      - ./:/var/www
+    depends_on:
+      - db
+      - memcached
+    command: sh -lc "while true; do php -d display_errors=0 bin/scheduler-run.php || true; sleep 60; done"
+    restart: unless-stopped
+
   db:
     image: mariadb:11.4
     env_file: