refactor(docker): docker-compose.yml ist der Pull-Weg, Bauen wandert nach .dev.yml

Namen getauscht: das Standard-Compose zieht jetzt die fertigen Registry-Images
(vorher docker-compose.prod.yml), die Build-Variante heisst docker-compose.dev.yml.
Weniger verwirrend, weil der Produktivfall ohne -f auskommt. Kopfkommentare,
README, CLAUDE.md, .env.example und build-push-images.mjs entsprechend angepasst.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docker-compose.yml

@@ -1,18 +1,16 @@
-# NovaSonic — builds locally from the Dockerfiles. The heavy deps (ffmpeg, Deno, yt-dlp, node libs)
-# are baked into the images, so container RESTARTS are instant, and a rebuild after a code change is
-# fast (Docker caches the dep layers — only the code COPY layer changes).
+# NovaSonic — Standard/Produktiv: zieht die fertigen Images aus der Registry, baut nichts.
+# Auf dem Server nur .env danebenlegen (siehe .env.example) und:
 #
-#   git pull
-#   docker compose up -d --build      # rebuild changed images (cached; fast) and (re)start
-#   docker compose up -d              # just (re)start with the already-built images
+#   docker compose pull
+#   docker compose up -d
 #
-# No registry needed. (An optional pull-from-registry / CI flow can build these same Dockerfiles
-# elsewhere and push — see scripts/build-push-images.mjs + .env.example.)
+# Die Images kommen von der Dev-Maschine: `npm run push-images` (baut die drei Dockerfiles und
+# pusht nach ${REGISTRY}). Selbst bauen statt ziehen: docker-compose.dev.yml.
 services:
 
   # ── Frontend (nginx serving the built PWA) ───────────────────────────────────
   novasonic-frontend:
-    build: .
+    image: ${REGISTRY}/novasonic-frontend:${TAG:-latest}
     container_name: novasonic-frontend
     restart: unless-stopped
     ports:
@@ -24,8 +22,7 @@ services:
 
   # ── Backend (yt-dlp download server) ─────────────────────────────────────────
   novasonic-backend:
-    build:
-      context: ./backend
+    image: ${REGISTRY}/novasonic-backend:${TAG:-latest}
     container_name: novasonic-backend
     restart: unless-stopped
     volumes:
@@ -48,10 +45,9 @@ services:
       - GITEA_TOKEN=${GITEA_TOKEN:-}
       - GITEA_APK_TAG=${GITEA_APK_TAG:-apk-latest}
 
-  # ── Scrobble service (isolated timestamped play-log → stats + Wrapped) ────────
+  # ── Scrobble service (isolated timestamped play-log → stats + Wrapped) ───────
   novasonic-scrobble:
-    build:
-      context: ./scrobble
+    image: ${REGISTRY}/novasonic-scrobble:${TAG:-latest}
     container_name: novasonic-scrobble
     restart: unless-stopped
     volumes: