chore(infra): simplify Docker builds and remove unused WEB_BUILD_PROFILE

- Adjusted Dockerfile’s build process for production-only artifacts.
- Removed unused `WEB_BUILD_PROFILE` from `dc-gui.yaml`.
- Optimized Gradle settings for better caching and performance.
- Updated `.dockerignore` to include source packages previously excluded by mistake.

dc-gui.yaml

@@ -16,7 +16,6 @@ services:
         # Frontend spezifisch:
         NODE_VERSION: "${DOCKER_NODE_VERSION:-24.12.0}"
         NGINX_IMAGE_TAG: "${DOCKER_NGINX_VERSION:-1.28.0-alpine}"
-        WEB_BUILD_PROFILE: "${WEB_BUILD_PROFILE:-dev}" # dev oder prod
         # Metadaten:
         VERSION: "${DOCKER_VERSION:-1.0.0-SNAPSHOT}"
         BUILD_DATE: "${DOCKER_BUILD_DATE}"