refactor(docker): make image-based the default compose, build variant is .dev

Less confusion: docker-compose.yml is now the default (pulls pre-built images)
and the build-on-host variant is docker-compose.dev.yml. Updated all references
(CLAUDE.md, README, .env.example, build-push-images.mjs, compose header).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docker-compose.prod.yml

@@ -1,63 +0,0 @@
-# Production stack — PULLS pre-built images instead of building on the host.
-#
-#   docker compose -f docker-compose.prod.yml pull
-#   docker compose -f docker-compose.prod.yml up -d
-#
-# Build & push the images from your dev machine with:  npm run push-images
-# (see scripts/build-push-images.mjs). Set REGISTRY + TAG in .env (see .env.example).
-services:
-
-  novasonic-frontend:
-    image: ${REGISTRY}/novasonic-frontend:${TAG:-latest}
-    pull_policy: always
-    container_name: novasonic-frontend
-    restart: unless-stopped
-    ports:
-      - "8080:80"
-    environment:
-      - NAVIDROME_URL=${NAVIDROME_URL}
-      - BACKEND_URL=${BACKEND_URL}
-      - SCROBBLE_URL=${SCROBBLE_URL}
-
-  novasonic-backend:
-    image: ${REGISTRY}/novasonic-backend:${TAG:-latest}
-    pull_policy: always
-    container_name: novasonic-backend
-    restart: unless-stopped
-    volumes:
-      - ${MUSIC_PATH}:${MUSIC_PATH}      # exact path from .env, no remapping
-      - novasonic-data:/data
-    ports:
-      - "3700:3700"
-    environment:
-      - PORT=3700
-      - MUSIC_PATH=${MUSIC_PATH}
-      - DATA_PATH=/data
-      - AUDIO_FMT=${AUDIO_FMT:-mp3}
-      - AUDIO_QUALITY=${AUDIO_QUALITY:-0}
-      - MAX_PARALLEL=${MAX_PARALLEL:-2}
-      - DOWNLOAD_BACKEND=${DOWNLOAD_BACKEND:-ytdlp}
-      - TICKETMASTER_API_KEY=${TICKETMASTER_API_KEY}
-      # Android APK download button — backend proxies the fixed Gitea release ("apk-latest").
-      - GITEA_URL=${GITEA_URL:-}
-      - GITEA_REPO=${GITEA_REPO:-}
-      - GITEA_TOKEN=${GITEA_TOKEN:-}
-      - GITEA_APK_TAG=${GITEA_APK_TAG:-apk-latest}
-
-  novasonic-scrobble:
-    image: ${REGISTRY}/novasonic-scrobble:${TAG:-latest}
-    pull_policy: always
-    container_name: novasonic-scrobble
-    restart: unless-stopped
-    volumes:
-      - novasonic-scrobble-data:/data
-    ports:
-      - "3710:3710"
-    environment:
-      - PORT=3710
-      - DATA_PATH=/data
-      - NAVIDROME_URL=${NAVIDROME_URL}   # for ping.view auth verification
-
-volumes:
-  novasonic-data:
-  novasonic-scrobble-data: