refactor(docker): default compose builds from Dockerfiles (baked deps, cached)

Chosen flow: build on the host from backend/scrobble Dockerfiles instead of
pulling from a registry (no registry / no Docker-on-dev needed). Heavy deps are
baked, so restarts are instant and rebuilds after git pull are cache-fast.
Removed the now-obsolete docker-compose.dev.yml (runtime-install variant); the
optional push-to-registry script stays for a future CI flow. Updated README,
CLAUDE.md, .env.example.

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

docker-compose.yml

@@ -1,33 +1,36 @@
-# Default (production) stack — PULLS pre-built images instead of building on the host.
+# 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).
 #
-#   docker compose pull
-#   docker compose up -d
+#   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
 #
-# 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).
-# To build on the host instead (dev), use docker-compose.dev.yml.
+# 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.)
 services:
 
+  # ── Frontend (nginx serving the built PWA) ───────────────────────────────────
   novasonic-frontend:
-    image: ${REGISTRY}/novasonic-frontend:${TAG:-latest}
-    pull_policy: always
+    build: .
     container_name: novasonic-frontend
     restart: unless-stopped
     ports:
-      - "8080:80"
+      - "8080:80"          # route this port through your reverse proxy
     environment:
-      - NAVIDROME_URL=${NAVIDROME_URL}
+      - NAVIDROME_URL=${NAVIDROME_URL}   # pre-filled on the setup screen
       - BACKEND_URL=${BACKEND_URL}
       - SCROBBLE_URL=${SCROBBLE_URL}
 
+  # ── Backend (yt-dlp download server) ─────────────────────────────────────────
   novasonic-backend:
-    image: ${REGISTRY}/novasonic-backend:${TAG:-latest}
-    pull_policy: always
+    build:
+      context: ./backend
     container_name: novasonic-backend
     restart: unless-stopped
     volumes:
       - ${MUSIC_PATH}:${MUSIC_PATH}      # exact path from .env, no remapping
-      - novasonic-data:/data
+      - novasonic-data:/data             # writable data dir for overrides, state, etc.
     ports:
       - "3700:3700"
     environment:
@@ -45,13 +48,14 @@ services:
       - GITEA_TOKEN=${GITEA_TOKEN:-}
       - GITEA_APK_TAG=${GITEA_APK_TAG:-apk-latest}
 
+  # ── Scrobble service (isolated timestamped play-log → stats + Wrapped) ────────
   novasonic-scrobble:
-    image: ${REGISTRY}/novasonic-scrobble:${TAG:-latest}
-    pull_policy: always
+    build:
+      context: ./scrobble
     container_name: novasonic-scrobble
     restart: unless-stopped
     volumes:
-      - novasonic-scrobble-data:/data
+      - novasonic-scrobble-data:/data    # own DB volume, isolated from downloads
     ports:
       - "3710:3710"
     environment: