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>

src/main.js

@@ -2,6 +2,7 @@ import { S } from './state.js';
 import { toast } from './utils.js';
 import { api, fetchRomajiIndex, loadRomajiOverrides } from './api.js';
 import { injectPWA } from './pwa.js';
+import { initPlayLog } from './player/scrobbleLog.js';
 import { loadSavedTheme } from './themes.js';
 import { initScrollRows } from './ui/components.js';
 import {
@@ -59,17 +60,18 @@ async function doConnect() {
   const _prev    = (() => { try { return JSON.parse(localStorage.getItem('ns_cfg') || '{}'); } catch { return {}; } })();
   const lfKey    = document.getElementById('lastfm-key')?.value.trim()   || _prev.lastfmKey  || '';
   const backUrl  = (document.getElementById('backend-url')?.value.trim() || _prev.backendUrl || window.NS_BACKEND_URL?.trim() || '').replace(/\/$/,'');
+  const scrobUrl = (_prev.scrobbleUrl || window.NS_SCROBBLE_URL?.trim() || '').replace(/\/$/,'');
   if(!url || !user || !pass) { _showSetupError('Bitte Server-URL, Benutzernamen und Passwort ausfüllen.'); return; }
   const btn = document.getElementById('btn-connect');
   btn.disabled=true; btn.textContent='Verbinde…';
   document.getElementById('setup-error').style.display='none';
-  S.cfg = {url, user, pass, lastfmKey:lfKey, backendUrl:backUrl};
+  S.cfg = {url, user, pass, lastfmKey:lfKey, backendUrl:backUrl, scrobbleUrl:scrobUrl};
   try {
     await api('ping');
     localStorage.setItem('ns_cfg', JSON.stringify(S.cfg));
     startApp();
   } catch(e) {
-    S.cfg = {url:'', user:'', pass:'', lastfmKey:'', backendUrl:''};
+    S.cfg = {url:'', user:'', pass:'', lastfmKey:'', backendUrl:'', scrobbleUrl:''};
     _showSetupError('Verbindung fehlgeschlagen: '+e.message);
     btn.disabled=false; btn.textContent='Verbinden';
   }
@@ -80,7 +82,7 @@ function disconnect() {
   localStorage.removeItem('ns_cfg');
   localStorage.removeItem('ns_last_played');
   sessionStorage.removeItem('ns_nav');
-  S.cfg = {url:'', user:'', pass:'', lastfmKey:'', backendUrl:''};
+  S.cfg = {url:'', user:'', pass:'', lastfmKey:'', backendUrl:'', scrobbleUrl:''};
   S.queue=[]; S.qIdx=-1; S._navStack=[]; S._navCursor=-1;
   S.audio.pause(); S.audio.src='';
   document.getElementById('app').style.display='none';
@@ -107,6 +109,7 @@ async function startApp() {
     navigate('home');
   }
   initNotifBell();
+  initPlayLog();   // flush any queued plays to the scrobble service (offline-safe)
   // Wait for overrides before restoring player bar so disp* functions have the cache ready
   loadRomajiOverrides().catch(() => {}).then(() => { _restoreLastPlayed(); });
   if(localStorage.getItem('ns_radio')==='1') { S.radioMode=true; _applyRadioBtn(); }
@@ -132,6 +135,7 @@ window.addEventListener('load', () => {
   if(saved) {
     S.cfg = JSON.parse(saved);
     if(!S.cfg.backendUrl && window.NS_BACKEND_URL?.trim()) S.cfg.backendUrl = window.NS_BACKEND_URL.trim().replace(/\/$/,'');
+    if(!S.cfg.scrobbleUrl && window.NS_SCROBBLE_URL?.trim()) S.cfg.scrobbleUrl = window.NS_SCROBBLE_URL.trim().replace(/\/$/,'');
     startApp();
     updateNpColorMode();
   }