switch away from registry usage for docker builds

.env.example

@@ -4,6 +4,13 @@ APP_KEY=
 APP_DEBUG=true
 APP_URL=http://localhost
 
+# Docker image tags (Dokploy/local build)
+APP_IMAGE_REPO=fotospiel-app
+APP_IMAGE_TAG=latest
+BUILD_CACHE_DIR=/var/lib/fotospiel-buildcache
+PHOTOBOOTH_CONTROL_IMAGE_REPO=fotospiel-photobooth-control
+PHOTOBOOTH_CONTROL_IMAGE_TAG=latest
+
 APP_LOCALE=en
 APP_FALLBACK_LOCALE=en
 APP_FAKER_LOCALE=en_US