feat(scrobble): own timestamped play-log service (stats/Wrapped foundation)

Phase 1+2 of a self-hosted, multi-user listening archive — the basis for
day/month/year stats and a yearly "Wrapped". Runs IN ADDITION to the existing
Navidrome/Last.fm scrobble; never replaces it.

Service (isolated, own container):
- scrobble/scrobble-server.js — node:sqlite play-log (own volume), routes
  POST /scrobble/plays (idempotent by uuid), GET /scrobble/history (archive),
  DELETE /scrobble/plays?user= (test cleanup), GET /scrobble/health.
  Multi-user auth via Navidrome ping.view (cached) -> user not spoofable.
- docker-compose: novasonic-scrobble service (node:22, port 3710) + volume;
  backend bumped node:20->22 (EOL); SCROBBLE_URL plumbing (entrypoint, .env.example).

Capture (both platforms, offline-safe queue, idempotent batch flush):
- Fires at the existing scrobbleMode counted-play moment — consistent with
  Last.fm, respects the user's setting (no separate 50%/4min rule).
- Web: src/player/scrobbleLog.js (localStorage queue) + subsonicAuthParams()
  in api.js + hooks in player.js + flush init in main.js; S.cfg.scrobbleUrl.
- Android: data/PlayLogClient.kt (filesDir queue, reused Ktor client) +
  repo.logPlay/flushPlayLog + PlayerController hook + NovaSonicApp flush +
  scrobbleUrl in PrefsStore/SettingsViewModel/SettingsScreen (with test button).

Plan + design decisions documented in docs/scrobble-plan.md.

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

docker-compose.yml

@@ -10,10 +10,11 @@ services:
     environment:
       - NAVIDROME_URL=${NAVIDROME_URL}   # pre-filled on the setup screen
       - BACKEND_URL=${BACKEND_URL}       # pre-filled on the setup screen
+      - SCROBBLE_URL=${SCROBBLE_URL}     # play-log / stats service (setup screen)
 
   # ── Backend (yt-dlp download server) ─────────────────────────────────────────
   novasonic-backend:
-    image: node:20-slim
+    image: node:22-slim
     container_name: novasonic-backend
     restart: unless-stopped
     working_dir: /app
@@ -41,5 +42,27 @@ services:
         cd /app && NODE_PATH=/deps/node_modules node novasonic-server.js
       "
 
+  # ── Scrobble service (isolated timestamped play-log → stats + Wrapped) ────────
+  novasonic-scrobble:
+    image: node:22-slim
+    container_name: novasonic-scrobble
+    restart: unless-stopped
+    working_dir: /app
+    volumes:
+      - ./scrobble:/app:ro               # server code (read-only)
+      - novasonic-scrobble-data:/data    # own DB volume, isolated from downloads
+    ports:
+      - "3710:3710"                      # route this port through your reverse proxy
+    environment:
+      - PORT=3710
+      - DATA_PATH=/data
+      - NAVIDROME_URL=${NAVIDROME_URL}   # for ping.view auth verification
+    command: >
+      sh -c "
+        mkdir -p /deps && cd /deps && npm install express &&
+        cd /app && NODE_PATH=/deps/node_modules node --experimental-sqlite scrobble-server.js
+      "
+
 volumes:
-  novasonic-data:    # persistent storage for romaji overrides and app state
+  novasonic-data:          # persistent storage for romaji overrides and app state
+  novasonic-scrobble-data: # persistent play-log DB (novasonic-plays.db)